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.*;
  
  /**
   * -----------------|___________|---------------------
   * CCCCCCCCC   OOOOOOOOOO   DDDDDDDD      EEEEEEEEE
   * CCCC        OOO    OOO   DD    DDD     EEEE
   * CCCC        OOO    OOO   DD     DDD    EEEEEEEEEE
   * CCCC        OOO    OOO   DD     DDDD   EEEE
   * CCCCCCCCC   OOOOOOOOOO   DDDDDDDDDDDD  EEEEEEEEEE
   * -----------------|___________|---------------------
   */
  
  public class Main {
      static long M = 1000000007;
  
      public static void main(String[] args) {
          InputStream inputStream = System.in;
          OutputStream outputStream = System.out;
          InputReader in = new InputReader(inputStream);
          PrintWriter sout = new PrintWriter(outputStream);
  
          int t = in.nextInt();
          while (t-- > 0) {
              long n = in.nextLong();
              long h = in.nextLong();
              long[] arr = new long[(int) n];
              for (int i = 0; i < n; i++) {
                  arr[i] = in.nextLong();
              }
              long right = h;
              long left = 0;
              while (left < right) {
                  long k = (left+right)/2; //возможно нужно будет изменить
                  long sum = k;
                  for(int i = 1; i<n; i++){
                      sum+= Math.min(k,arr[i]-arr[i-1]);
                  }
                  if(sum<h){
                      left = k+1;
                  } else {
                      right = k;
                  }
              }
              sout.println(right);
          }
          sout.close();
      }
  
      private static class Pair {
          int x;
          int y;
  
          public Pair(int x, int y) {
              this.x = x;
              this.y = y;
          }
      }
  
      public static long factorial(long N) {
          long result = 1;
          for (long x = 2; x <= N; x++) {
              result = (result * x) % M;
          }
          return result;
      }
  
      public static long binomial(long n) {
          long nom = factorial(n); // n!
          long denom = ((long) 2 * factorial(n - 2)) % M; // k!(n-k)!
          return (nom * fastPow(denom, M - 2)) % M;
      }
  
      public static long fastPow(long num, long pow) {
          if (pow == 0)
              return 1;
          if (pow % 2 == 0) {
              long result = fastPow(num, pow / 2);
              result = (result * result) % M;
              return result;
          }
          long result = fastPow(num, pow - 1);
          result = (result * num) % M;
          return result;
      }
  
  
      public static void sortLong(long[] a) {
          ArrayList<Long> l = new ArrayList<>();
          for (long i : a)
              l.add(i);
          Collections.sort(l);
          for (int i = 0; i < a.length; i++)
              a[i] = l.get(i);
      }
  
      public static void sortInt(int[] a) {
          ArrayList<Integer> l = new ArrayList<>();
          for (int i : a)
              l.add(i);
          Collections.sort(l);
          for (int i = 0; i < a.length; i++)
              a[i] = l.get(i);
      }
  
      public static class Node {
          int value;
          boolean visit = false;
          List<Node> neighbors = new ArrayList<>();
  
          public Node(int value) {
              this.value = value;
          }
      }
  
      public static class InputReader {
          private final BufferedReader reader;
          private StringTokenizer tokenizer;
  
          public InputReader(InputStream stream) {
              reader = new BufferedReader(new InputStreamReader(stream), 32768);
              tokenizer = null;
          }
  
          public String nextToken() {
              while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                  try {
                      tokenizer = new StringTokenizer(reader.readLine());
                  } catch (IOException e) {
                      throw new RuntimeException(e);
                  }
              }
              return tokenizer.nextToken();
          }
  
          public int nextInt() {
              return Integer.parseInt(nextToken());
          }
  
          public long nextLong() {
              return Long.parseLong(nextToken());
          }
  
          public double nextDouble() {
              return Double.parseDouble(nextToken());
          }
      }
  }