description: Lord Omkar would like to have a tree with n nodes (3 ≤ n ≤ 10^5) and has asked his disciples to construct the tree. However, Lord Omkar has created m (1 ≤ m < n) restrictions to ensure that the tree will be as heavenly as possible. 
  
  A tree with n nodes is an connected undirected graph with n nodes and n-1 edges. Note that for any two nodes, there is exactly one simple path between them, where a simple path is a path between two nodes that does not contain any node more than once.
  
  Here is an example of a tree: 
  
  <image>
  
  A restriction consists of 3 pairwise distinct integers, a, b, and c (1 ≤ a,b,c ≤ n). It signifies that node b cannot lie on the simple path between node a and node c. 
  
  Can you help Lord Omkar and become his most trusted disciple? You will need to find heavenly trees for multiple sets of restrictions. It can be shown that a heavenly tree will always exist for any set of restrictions under the given constraints.
  
  Input
  
  Each test contains multiple test cases. The first line contains the number of test cases t (1 ≤ t ≤ 10^4). Description of the test cases follows.
  
  The first line of each test case contains two integers, n and m (3 ≤ n ≤ 10^5, 1 ≤ m < n), representing the size of the tree and the number of restrictions.
  
  The i-th of the next m lines contains three integers a_i, b_i, c_i (1 ≤ a_i, b_i, c_i ≤ n, a, b, c are distinct), signifying that node b_i cannot lie on the simple path between nodes a_i and c_i. 
  
  It is guaranteed that the sum of n across all test cases will not exceed 10^5.
  
  Output
  
  For each test case, output n-1 lines representing the n-1 edges in the tree. On each line, output two integers u and v (1 ≤ u, v ≤ n, u ≠ v) signifying that there is an edge between nodes u and v. Given edges have to form a tree that satisfies Omkar's restrictions.
  
  Example
  
  Input
  
  
  2
  7 4
  1 2 3
  3 4 5
  5 6 7
  6 5 4
  5 3
  1 2 3
  2 3 4
  3 4 5
  
  
  Output
  
  
  1 2
  1 3
  3 5
  3 4
  2 7
  7 6
  5 1
  1 3
  3 2
  2 4
  
  Note
  
  The output of the first sample case corresponds to the following tree: 
  
  <image> For the first restriction, the simple path between 1 and 3 is 1, 3, which doesn't contain 2. The simple path between 3 and 5 is 3, 5, which doesn't contain 4. The simple path between 5 and 7 is 5, 3, 1, 2, 7, which doesn't contain 6. The simple path between 6 and 4 is 6, 7, 2, 1, 3, 4, which doesn't contain 5. Thus, this tree meets all of the restrictions.
  
  The output of the second sample case corresponds to the following tree: 
  
  <image>
solution: import java.util.*;
  import java.io.*;
  
  public class Main {
  
      static long startTime = System.currentTimeMillis();
  
      // for global initializations and methods starts here
  
      // global initialisations and methods end here
  
      static void run() {
          boolean tc = true;
          AdityaFastIO r = new AdityaFastIO();
          //FastReader r = new FastReader();
  
          try (OutputStream out = new BufferedOutputStream(System.out)) {
  
              //long startTime = System.currentTimeMillis();
  
              int testcases = tc ? r.ni() : 1;
              int tcCounter = 1;
              // Hold Here Sparky------------------->>>
              // Solution Starts Here
  
              start:
              while (testcases-- > 0) {
  
                  int n = r.ni();
                  int m = r.ni();
  
                  Set<Integer> set = new HashSet<>();
                  for (int i = 1; i <= n; i++) set.add(i);
  
                  while (m-- > 0) {
                      int u = r.ni();
                      int v = r.ni();
                      int w = r.ni();
  
                      set.remove(v); // remove middle
                  }
  
                  int get = set.stream().findFirst().get();
                  for (int i = 1; i <= n; i++) {
                      if (i == get) continue;
                      out.write((get + " " + i + " ").getBytes());
                      out.write(("\n").getBytes());
                  }
  
              }
              // Solution Ends Here
          } catch (IOException e) {
              e.printStackTrace();
          }
      }
  
      static class AdityaFastIO {
          final private int BUFFER_SIZE = 1 << 16;
          private final DataInputStream din;
          private final byte[] buffer;
          private int bufferPointer, bytesRead;
          public BufferedReader br;
          public StringTokenizer st;
  
          public AdityaFastIO() {
              br = new BufferedReader(new InputStreamReader(System.in));
              din = new DataInputStream(System.in);
              buffer = new byte[BUFFER_SIZE];
              bufferPointer = bytesRead = 0;
          }
  
          public AdityaFastIO(String file_name) throws IOException {
              din = new DataInputStream(new FileInputStream(file_name));
              buffer = new byte[BUFFER_SIZE];
              bufferPointer = bytesRead = 0;
          }
  
          public String word() {
              while (st == null || !st.hasMoreElements()) {
                  try {
                      st = new StringTokenizer(br.readLine());
                  } catch (IOException e) {
                      e.printStackTrace();
                  }
              }
              return st.nextToken();
          }
  
          public String line() {
              String str = "";
              try {
                  str = br.readLine();
              } catch (IOException e) {
                  e.printStackTrace();
              }
              return str;
          }
  
          public String readLine() throws IOException {
              byte[] buf = new byte[100000001]; // line length
              int cnt = 0, c;
              while ((c = read()) != -1) {
                  if (c == '\n') break;
                  buf[cnt++] = (byte) c;
              }
              return new String(buf, 0, cnt);
          }
  
          public int ni() throws IOException {
              int ret = 0;
              byte c = read();
              while (c <= ' ') c = read();
              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 nl() throws IOException {
              long ret = 0;
              byte c = read();
              while (c <= ' ') c = read();
              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 nd() throws IOException {
              double ret = 0, div = 1;
              byte c = read();
              while (c <= ' ') c = read();
              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();
          }
      }
  
      public static void main(String[] args) throws Exception {
          run();
      }
  
      static long mod = 998244353;
  
      static long modInv(long base, long e) {
          long result = 1;
          base %= mod;
          while (e > 0) {
              if ((e & 1) > 0) result = result * base % mod;
              base = base * base % mod;
              e >>= 1;
          }
          return result;
      }
  
      static class FastReader {
          BufferedReader br;
          StringTokenizer st;
  
          public FastReader() {
              br = new BufferedReader(new InputStreamReader(System.in));
          }
  
          String word() {
              while (st == null || !st.hasMoreElements()) {
                  try {
                      st = new StringTokenizer(br.readLine());
                  } catch (IOException e) {
                      e.printStackTrace();
                  }
              }
              return st.nextToken();
          }
  
          String line() {
              String str = "";
              try {
                  str = br.readLine();
              } catch (IOException e) {
                  e.printStackTrace();
              }
              return str;
          }
  
          int ni() {
              return Integer.parseInt(word());
          }
  
          long nl() {
              return Long.parseLong(word());
          }
  
          double nd() {
              return Double.parseDouble(word());
          }
      }
  
      static int MOD = (int) (1e9 + 7);
  
      static long powerLL(long x, long n) {
          long result = 1;
          while (n > 0) {
              if (n % 2 == 1) result = result * x % MOD;
              n = n / 2;
              x = x * x % MOD;
          }
          return result;
      }
  
      static long powerStrings(int i1, int i2) {
          String sa = String.valueOf(i1);
          String sb = String.valueOf(i2);
          long a = 0, b = 0;
          for (int i = 0; i < sa.length(); i++) a = (a * 10 + (sa.charAt(i) - '0')) % MOD;
          for (int i = 0; i < sb.length(); i++) b = (b * 10 + (sb.charAt(i) - '0')) % (MOD - 1);
          return powerLL(a, b);
      }
  
      static long gcd(long a, long b) {
          if (a == 0) return b;
          else return gcd(b % a, a);
      }
  
      static long lcm(long a, long b) {
          return (a * b) / gcd(a, b);
      }
  
      static long lower_bound(int[] arr, int x) {
          int l = -1, r = arr.length;
          while (l + 1 < r) {
              int m = (l + r) >>> 1;
              if (arr[m] >= x) r = m;
              else l = m;
          }
          return r;
      }
  
      static int upper_bound(int[] arr, int x) {
          int l = -1, r = arr.length;
          while (l + 1 < r) {
              int m = (l + r) >>> 1;
              if (arr[m] <= x) l = m;
              else r = m;
          }
          return l + 1;
      }
  
      static void addEdge(ArrayList<ArrayList<Integer>> graph, int edge1, int edge2) {
          graph.get(edge1).add(edge2);
          graph.get(edge2).add(edge1);
      }
  
      public static class Pair implements Comparable<Pair> {
          int first;
          int second;
  
          public Pair(int first, int second) {
              this.first = first;
              this.second = second;
          }
  
          public String toString() {
              return "(" + first + "," + second + ")";
          }
  
          public int compareTo(Pair o) {
              // TODO Auto-generated method stub
              if (this.first != o.first)
                  return (int) (this.first - o.first);
              else return (int) (this.second - o.second);
          }
      }
  
      public static class PairC<X, Y> implements Comparable<PairC> {
          X first;
          Y second;
  
          public PairC(X first, Y second) {
              this.first = first;
              this.second = second;
          }
  
          public String toString() {
              return "(" + first + "," + second + ")";
          }
  
          public int compareTo(PairC o) {
              // TODO Auto-generated method stub
              return o.compareTo((PairC) first);
          }
      }
  
      static boolean isCollectionsSorted(List<Long> list) {
          if (list.size() == 0 || list.size() == 1) return true;
          for (int i = 1; i < list.size(); i++) if (list.get(i) <= list.get(i - 1)) return false;
          return true;
      }
  
      static boolean isCollectionsSortedReverseOrder(List<Long> list) {
          if (list.size() == 0 || list.size() == 1) return true;
          for (int i = 1; i < list.size(); i++) if (list.get(i) >= list.get(i - 1)) return false;
          return true;
      }
  
  } 