description: Polycarp has come up with a new game to play with you. He calls it "A missing bigram".
  
  A bigram of a word is a sequence of two adjacent letters in it.
  
  For example, word "abbaaba" contains bigrams "ab", "bb", "ba", "aa", "ab" and "ba".
  
  The game goes as follows. First, Polycarp comes up with a word, consisting only of lowercase letters 'a' and 'b'. Then, he writes down all its bigrams on a whiteboard in the same order as they appear in the word. After that, he wipes one of them off the whiteboard.
  
  Finally, Polycarp invites you to guess what the word that he has come up with was.
  
  Your goal is to find any word such that it's possible to write down all its bigrams and remove one of them, so that the resulting sequence of bigrams is the same as the one Polycarp ended up with.
  
  The tests are generated in such a way that the answer exists. If there are multiple answers, you can print any of them.
  
  Input
  
  The first line contains a single integer t (1 ≤ t ≤ 2000) — the number of testcases.
  
  The first line of each testcase contains a single integer n (3 ≤ n ≤ 100) — the length of the word Polycarp has come up with.
  
  The second line of each testcase contains n-2 bigrams of that word, separated by a single space. Each bigram consists of two letters, each of them is either 'a' or 'b'.
  
  Additional constraint on the input: there exists at least one string such that it is possible to write down all its bigrams, except one, so that the resulting sequence is the same as the sequence in the input. In other words, the answer exists.
  
  Output
  
  For each testcase print a word, consisting of n letters, each of them should be either 'a' or 'b'. It should be possible to write down all its bigrams and remove one of them, so that the resulting sequence of bigrams is the same as the one Polycarp ended up with.
  
  The tests are generated in such a way that the answer exists. If there are multiple answers, you can print any of them. 
  
  Example
  
  Input
  
  
  4
  7
  ab bb ba aa ba
  7
  ab ba aa ab ba
  3
  aa
  5
  bb ab bb
  
  
  Output
  
  
  abbaaba
  abaabaa
  baa
  bbabb
  
  Note
  
  The first two testcases from the example are produced from the word "abbaaba". As listed in the statement, it contains bigrams "ab", "bb", "ba", "aa", "ab" and "ba".
  
  In the first testcase, the 5-th bigram is removed. 
  
  In the second testcase, the 2-nd bigram is removed. However, that sequence could also have been produced from the word "abaabaa". It contains bigrams "ab", "ba", "aa", "ab", "ba" and "aa". The missing bigram is the 6-th one.
  
  In the third testcase, all of "baa", "aab" and "aaa" are valid answers.
solution: import java.io.*;
  import java.util.*;
  import java.util.ArrayList;
  import java.util.Arrays.*;
  import java.util.Map.Entry;
  
  import static java.util.Collections.*;
  import static java.lang.Integer.parseInt;
  import static java.lang.Math.*;
  import static java.lang.String.format;
  import static java.util.Arrays.*;
  
  public class CC {
      static final int SCAN_LINE_LENGTH = 1_000_002;
      private static final boolean thread = false;
      @SuppressWarnings("all")
      static final boolean HAS_TEST_CASES = (1 == 1) ? true : false;
  
      static int n, a[], e[][], vis[], m, b[];
      @SuppressWarnings("all")
      private static ArrayList<Integer> adj[], v = new ArrayList<>();
      static long gcd = 1;
      static HashMap<Integer, Integer> pos;
  
      @SuppressWarnings("unchecked")
      static void solve() throws Exception {
          n = ni();
          char ns[][] = new char[n - 2][2];
          for (int i = 0; i < ns.length; i++) {
              ns[i] = ns();
          }
          StringBuffer sb = new StringBuffer();
          boolean f = true;
          sb.append(ns[0][0]);
          for (int i = 0; i < ns.length - 1; i++) {
              sb.append(ns[i][1]);
              if (ns[i][1] != ns[i + 1][0]) {
                  f = false;
                  sb.append(ns[i + 1][0]);
              }
          }
          if (f)
              sb.append(ns[ns.length - 1][1]);
          sb.append(ns[ns.length - 1][1]);
          pn(sb.toString());
      }
  
      public static void main(final String[] args) throws Exception {
          if (!thread) {
              final int TEST_CASES = HAS_TEST_CASES ? ni() : 1;
              for (int i = 1; i <= TEST_CASES; i++) {
                  // pni(i + " t");
                  // out.print("Case #" + (i) + ": ");
                  try {
                      solve();
                  } catch (final Exception e) {
                      // pni("idk Exception");
                      // e.printStackTrace(System.err);
                      // System.exit(0);
                      throw e;
                  }
              }
              out.flush();
          }
          r.close();
          out.close();
      }
  
      @SuppressWarnings("all")
      private static final int MOD = (int) (1e9 + 7), MOD_FFT = 998244353;
      private static final Reader r = new Reader();
      @SuppressWarnings("all")
      private static final int[][] GRID_DIRECTION_4 = { { 1, 0 }, { -1, 0 }, { 0, 1 }, { 0, -1 } };
      @SuppressWarnings("all")
      private static final int[][] GRID_DIRECTION_ALL = { { 1, 0 }, { -1, 0 }, { 0, 1 }, { 0, -1 }, { 1, 1 }, { -1, 1 },
              { 1, -1 }, { -1, -1 } };
      private static final PrintWriter out = new PrintWriter(new BufferedOutputStream(System.out));
      private static int[] deepCopy;
  
      public static long[] enumPows(int a, final int n, final int mod) {
          a %= mod;
          final long[] pows = new long[n + 1];
          pows[0] = 1;
          for (int i = 1; i <= n; i++)
              pows[i] = pows[i - 1] * a % mod;
          return pows;
      }
  
      @SuppressWarnings("all")
      private static ArrayList<Integer> sieve(final int n) {
          final ArrayList<Integer> p = new ArrayList<>();
          final int[] f = new int[n + 1];
          for (int i = 2; i <= n; i++) {
              if (f[i] == 1)
                  continue;
              for (int j = i * i; j <= n && j < f.length; j += i) {
                  f[j] = 1;
              }
          }
          for (int i = 2; i < f.length; i++) {
              if (f[i] == 0)
                  p.add(i);
          }
          return p;
      }
  
      @SuppressWarnings("all")
      private static void s(final int[] a) {
          final Integer[] t = new Integer[a.length];
          for (int i = 0; i < t.length; i++) {
              t[i] = a[i];
          }
          sort(t);
          for (int i = 0; i < t.length; i++) {
              a[i] = t[i];
          }
      }
  
      int pow(int a, int b, final int m) {
          int ans = 1;
          while (b != 0) {
              if ((b & 1) != 0)
                  ans = (ans * a) % m;
              b /= 2;
              a = (a * a) % m;
          }
          return ans;
      }
  
      int modInverse(final int k) {
          return pow(k, MOD - 2, MOD);
      }
  
      @SuppressWarnings("all")
      private static void swap(final int i, final int j) {
          final int temp = a[i];
          a[i] = a[j];
          a[j] = temp;
      }
  
      @SuppressWarnings("all")
      private static boolean isMulOverflow(final long A, final long B) {
          if (A == 0 || B == 0)
              return false;
          final long result = A * B;
          if (A == result / B)
              return true;
          return false;
      }
  
      @SuppressWarnings("all")
      private static int gcd(final int a, final int b) {
          if (b == 0)
              return a;
          return gcd(b, a % b);
      }
  
      @SuppressWarnings("all")
      private static long gcd(final long a, final long b) {
          if (b == 0)
              return a;
          return gcd(b, a % b);
      }
  
      @SuppressWarnings("all")
      private static class Pair<T, E> implements Comparable<Pair<T, E>> {
          T fir;
          E snd;
  
          Pair() {
          }
  
          Pair(final T x, final E y) {
              this.fir = x;
              this.snd = y;
          }
  
          /*
           * (non-Javadoc)
           * 
           * @see java.lang.Object#hashCode()
           */
  
          /*
           * (non-Javadoc)
           * 
           * @see java.lang.Object#toString()
           */
  
          @Override
          public String toString() {
              return "Pair [fir = " + fir + ", snd = " + snd + "]";
          }
  
          @Override
          public int hashCode() {
              final int prime = 31;
              int result = 1;
              result = prime * result + ((fir == null) ? 0 : fir.hashCode());
              result = prime * result + ((snd == null) ? 0 : snd.hashCode());
              return result;
          }
  
          /*
           * (non-Javadoc)
           * 
           * @see java.lang.Object#equals(java.lang.Object)
           */
  
          @Override
          public boolean equals(final Object obj) {
              if (this == obj)
                  return true;
              if (obj == null)
                  return false;
              if (getClass() != obj.getClass())
                  return false;
              final Pair other = (Pair) obj;
              if (fir == null) {
                  if (other.fir != null)
                      return false;
              } else if (!fir.equals(other.fir))
                  return false;
              if (snd == null) {
                  if (other.snd != null)
                      return false;
              } else if (!snd.equals(other.snd))
                  return false;
              return true;
          }
  
          /**
           * @return the fir
           */
          public T getFir() {
              return fir;
          }
  
          /**
           * @param fir the fir to set
           */
          public void setFir(final T fir) {
              this.fir = fir;
          }
  
          /**
           * @return the snd
           */
          public E getSnd() {
              return snd;
          }
  
          /**
           * @param snd the snd to set
           */
          public void setSnd(final E snd) {
              this.snd = snd;
          }
  
          @Override
          @SuppressWarnings("unchecked")
          public int compareTo(final Pair<T, E> o) {
              final int c = ((Comparable<T>) fir).compareTo(o.fir);
              return c != 0 ? c : ((Comparable<E>) snd).compareTo(o.snd);
          }
          // @Override
          // @SuppressWarnings("unchecked")
          // public int compareTo(final Pair<T, E> o) {
          // final int c = ((Comparable<T>) fir).compareTo(o.fir);
          // return c;
          // }
  
      }
  
      @SuppressWarnings("all")
      private static class pi implements Comparable<pi> {
          int fir, snd;
  
          pi() {
          }
  
          pi(final int a, final int b) {
              fir = a;
              snd = b;
          }
  
          public int compareTo(final pi o) {
              return fir == o.fir ? snd - o.snd : fir - o.fir;
          }
  
          @Override
          public int hashCode() {
              final int prime = 31;
              int result = 1;
              result = prime * result + fir;
              result = prime * result + snd;
              return result;
          }
  
          @Override
          public boolean equals(final Object obj) {
              if (this == obj)
                  return true;
              if (obj == null)
                  return false;
              if (getClass() != obj.getClass())
                  return false;
              final pi other = (pi) obj;
              if (fir != other.fir)
                  return false;
              if (snd != other.snd)
                  return false;
              return true;
          }
  
      }
  
      @SuppressWarnings("all")
      private static <T> void checkV(final Vector<T> adj[], final int i) {
          adj[i] = adj[i] == null ? new Vector<>() : adj[i];
      }
  
      @SuppressWarnings("all")
      private static <T> void checkV(final ArrayList<T> adj[], final int i) {
          adj[i] = adj[i] == null ? new ArrayList<>() : adj[i];
      }
  
      @SuppressWarnings("all")
      private static int[] na(final int n) throws Exception {
          final int[] a = new int[n];
          for (int i = 0; i < n; i++) {
              a[i] = ni();
          }
          return a;
      }
  
      @SuppressWarnings("all")
      private static int[] na1(final int n) throws Exception {
          final int[] a = new int[n + 1];
          for (int i = 1; i < a.length; i++) {
              a[i] = ni();
          }
          return a;
      }
  
      @SuppressWarnings("all")
      private static String n() throws IOException {
          return r.readToken();
      }
  
      @SuppressWarnings("all")
      private static char[] ns() throws IOException {
          return r.readToken().toCharArray();
      }
  
      @SuppressWarnings("all")
      private static String nln() throws IOException {
          return r.readLine();
      }
  
      private static int ni() throws IOException {
          return r.nextInt();
      }
  
      @SuppressWarnings("all")
      private static long nl() throws IOException {
          return r.nextLong();
      }
  
      @SuppressWarnings("all")
      private static double nd() throws IOException {
          return r.nextDouble();
      }
  
      @SuppressWarnings("all")
      private static void p(final Object o) {
          out.print(o);
      }
  
      @SuppressWarnings("all")
      private static void pn(final Object o) {
          out.println(o);
      }
  
      @SuppressWarnings("all")
      private static void pn() {
          out.println("");
      }
  
      @SuppressWarnings("all")
      private static void pi(final Object o) {
          out.print(o);
          out.flush();
      }
  
      @SuppressWarnings("all")
      private static void pni() {
          out.println("");
          out.flush();
      }
  
      private static void pni(final Object o) {
          out.println(o);
          out.flush();
      }
  
      private static class Reader {
          private final int BUFFER_SIZE = 1 << 17;
          private final DataInputStream din;
          private final byte[] buffer;
          private int bufferPointer, bytesRead;
          // private StringTokenizer st;
  
          public Reader() {
              din = new DataInputStream(System.in);
              buffer = new byte[BUFFER_SIZE];
              bufferPointer = bytesRead = 0;
          }
  
          @SuppressWarnings("all")
          public Reader(final String file_name) throws IOException {
              din = new DataInputStream(new FileInputStream(file_name));
              buffer = new byte[BUFFER_SIZE];
              bufferPointer = bytesRead = 0;
          }
  
          final byte[] buf = new byte[SCAN_LINE_LENGTH];
  
          public String readLine() throws IOException {
              int cnt = 0;
              int c;
              o: while ((c = read()) != -1) {
                  if (c == '\n')
                      if (cnt == 0)
                          continue o;
                      else
                          break;
                  buf[cnt++] = (byte) c;
              }
              return new String(buf, 0, cnt);
          }
  
          public String readToken() throws IOException {
              int cnt = 0;
              int c;
              o: while ((c = read()) != -1) {
                  if (!(c >= 33 && c <= 126))
                      if (cnt == 0)
                          continue o;
                      else
                          break;
                  buf[cnt++] = (byte) c;
              }
              return new String(buf, 0, cnt);
          }
  
          public int nextInt() throws IOException {
              int ret = 0;
              byte c = read();
              while (c <= ' ')
                  c = read();
              final boolean neg = (c == '-');
              if (neg)
                  c = read();
              do {
                  ret = ret * 10 + c - '0';
              } while ((c = read()) >= '0' && c <= '9');
  
              if (neg)
                  return -ret;
              return ret;
          }
  
          public long nextLong() throws IOException {
              long ret = 0;
              byte c = read();
              while (c <= ' ')
                  c = read();
              final boolean neg = (c == '-');
              if (neg)
                  c = read();
              do {
                  ret = ret * 10 + c - '0';
              } while ((c = read()) >= '0' && c <= '9');
              if (neg)
                  return -ret;
              return ret;
          }
  
          public double nextDouble() throws IOException {
              double ret = 0, div = 1;
              byte c = read();
              while (c <= ' ')
                  c = read();
              final boolean neg = (c == '-');
              if (neg)
                  c = read();
  
              do {
                  ret = ret * 10 + c - '0';
              } while ((c = read()) >= '0' && c <= '9');
  
              if (c == '.') {
                  while ((c = read()) >= '0' && c <= '9') {
                      ret += (c - '0') / (div *= 10);
                  }
              }
  
              if (neg)
                  return -ret;
              return ret;
          }
  
          private void fillBuffer() throws IOException {
              bytesRead = din.read(buffer, bufferPointer = 0, BUFFER_SIZE);
              if (bytesRead == -1)
                  buffer[0] = -1;
          }
  
          private byte read() throws IOException {
              if (bufferPointer == bytesRead)
                  fillBuffer();
              return buffer[bufferPointer++];
          }
  
          public void close() throws IOException {
              if (din == null)
                  return;
              din.close();
          }
      }
  
      // static {
      // if (thread)
      // new Thread(null, new Runnable() {
      // @Override
      // public void run() {
      // try {
      // final int testCases = HAS_TEST_CASES ? ni() : 1;
      // for (int i = 1; i <= testCases; i++) {
      // // out.print("Case #" + (i + 1) + ": ");
      // try {
      // solve();
      // } catch (final ArrayIndexOutOfBoundsException e) {
      // e.printStackTrace(System.err);
      // System.exit(-1);
      // } catch (final Exception e) {
      // pni("idk Exception in solve");
      // e.printStackTrace(System.err);
      // System.exit(-1);
      // }
      // }
      // out.flush();
      // } catch (final Throwable t) {
      // t.printStackTrace(System.err);
      // System.exit(-1);
      // }
      // }
      // }, "rec", (1L << 28)).start();
      // }
  
      @SuppressWarnings({ "all", })
      private static <T> T deepCopy(final T old) {
          try {
              return (T) deepCopyObject(old);
          } catch (final IOException | ClassNotFoundException e) {
              e.printStackTrace(System.err);
              System.exit(-1);
          }
          return null;
      }
  
      private static Object deepCopyObject(final Object oldObj) throws IOException, ClassNotFoundException {
          ObjectOutputStream oos = null;
          ObjectInputStream ois = null;
          try {
              final ByteArrayOutputStream bos = new ByteArrayOutputStream(); // A
              oos = new ObjectOutputStream(bos); // B
              // serialize and pass the object
              oos.writeObject(oldObj); // C
              oos.flush(); // D
              final ByteArrayInputStream bin = new ByteArrayInputStream(bos.toByteArray()); // E
              ois = new ObjectInputStream(bin); // F
              // return the new object
              return ois.readObject(); // G
          } catch (final ClassNotFoundException e) {
              pni("Exception while Object Cloning = " + e);
              throw (e);
          } finally {
              oos.close();
              ois.close();
          }
      }
  
  }