description: Monocarp is playing yet another computer game. In this game, his character has to kill a dragon. The battle with the dragon lasts 100^{500} seconds, during which Monocarp attacks the dragon with a poisoned dagger. The i-th attack is performed at the beginning of the a_i-th second from the battle start. The dagger itself does not deal damage, but it applies a poison effect on the dragon, which deals 1 damage during each of the next k seconds (starting with the same second when the dragon was stabbed by the dagger). However, if the dragon has already been poisoned, then the dagger updates the poison effect (i.e. cancels the current poison effect and applies a new one).
  
  For example, suppose k = 4, and Monocarp stabs the dragon during the seconds 2, 4 and 10. Then the poison effect is applied at the start of the 2-nd second and deals 1 damage during the 2-nd and 3-rd seconds; then, at the beginning of the 4-th second, the poison effect is reapplied, so it deals exactly 1 damage during the seconds 4, 5, 6 and 7; then, during the 10-th second, the poison effect is applied again, and it deals 1 damage during the seconds 10, 11, 12 and 13. In total, the dragon receives 10 damage.
  
  Monocarp knows that the dragon has h hit points, and if he deals at least h damage to the dragon during the battle — he slays the dragon. Monocarp has not decided on the strength of the poison he will use during the battle, so he wants to find the minimum possible value of k (the number of seconds the poison effect lasts) that is enough to deal at least h damage to the dragon.
  
  Input
  
  The first line contains a single integer t (1 ≤ t ≤ 1000) — the number of test cases.
  
  The first line of the test case contains two integers n and h (1 ≤ n ≤ 100; 1 ≤ h ≤ 10^{18}) — the number of Monocarp's attacks and the amount of damage that needs to be dealt.
  
  The second line contains n integers a_1, a_2, ..., a_n (1 ≤ a_i ≤ 10^9; a_i < a_{i + 1}), where a_i is the second when the i-th attack is performed.
  
  Output
  
  For each test case, print a single integer — the minimum value of the parameter k, such that Monocarp will cause at least h damage to the dragon.
  
  Example
  
  Input
  
  
  4
  2 5
  1 5
  3 10
  2 4 10
  5 3
  1 2 4 5 7
  4 1000
  3 25 64 1337
  
  
  Output
  
  
  3
  4
  1
  470
  
  Note
  
  In the first example, for k=3, damage is dealt in seconds [1, 2, 3, 5, 6, 7].
  
  In the second example, for k=4, damage is dealt in seconds [2, 3, 4, 5, 6, 7, 10, 11, 12, 13].
  
  In the third example, for k=1, damage is dealt in seconds [1, 2, 4, 5, 7].
solution: import java.io.*;
  import java.util.*;
  import java.util.ArrayList;
  import java.util.Arrays.*;
  import java.util.Map.Entry;
  
  import org.xml.sax.InputSource;
  
  import static java.util.Collections.*;
  import static java.lang.Math.*;
  import static java.util.Arrays.*;
  
  public class Main {
      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();
          long h = nl();
          a = na(n);
          long[] diff = new long[a.length - 1];
          for (int i = 0; i < diff.length; i++) {
              diff[i] = a[i + 1] - a[i];
          }
          s(diff);
          long th = 0;
          long k = 0;
          for (int i = 0; i < diff.length; i++) {
              long t = ((long) (n - i)) * (diff[i] - (i == 0 ? 0 : diff[i - 1]));
              if (th + t <= h) {
                  th += t;
                  k = diff[i];
              } else if (th + t > h) {
                  long d = (long) Math.ceil((double) (h - th) / (n - i));
                  k += d;
                  th += d * (n - i);
                  break;
              }
          }
          if (th < h) {
              k += h - th;
          }
          pn(k);
      }
  
      public static void main(final String[] args) throws Exception {
          if (!thread) {
              final int testcases = HAS_TEST_CASES ? ni() : 1;
              for (int i = 1; i <= testcases; 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();
      private static final PrintWriter out = new PrintWriter(new BufferedOutputStream(System.out));
  
      public static long[] enumPows(int a, int n, int mod) {
          a %= mod;
          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> seive(int n) {
          ArrayList<Integer> p = new ArrayList<>();
          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(long[] a) {
          Long[] t = new Long[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];
          }
      }
  
      @SuppressWarnings("all")
      private static void s(int[] a) {
          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, 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 modinv(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;
          }
  
          // @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(Object obj) {
              if (this == obj)
                  return true;
              if (obj == null)
                  return false;
              if (getClass() != obj.getClass())
                  return false;
              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];
      }
  
      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 in ObjectCloner = " + e);
              throw (e);
          } finally {
              oos.close();
              ois.close();
          }
      }
  
  }