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: //
  // Source code recreated from a .class file by IntelliJ IDEA
  // (powered by Fernflower decompiler)
  //
  
  import javax.swing.plaf.basic.BasicInternalFrameTitlePane;
  import java.io.BufferedWriter;
  import java.io.DataInputStream;
  import java.io.FileInputStream;
  import java.io.IOException;
  import java.io.OutputStreamWriter;
  import java.util.*;
  
  public class CFC {
      static CFC.Reader sc = new CFC.Reader();
      static BufferedWriter bw;
      static int team1;
      static int team2;
      static int minkicks;
  
      public CFC() {
      }
  
      public static void main(String[] args) throws IOException {
          Scanner sc = new Scanner(System.in);
          int t = inputInt();
          process:
          for (int p = 0; p < t; p++) {
              int n=inputInt();
              long h=inputLong();
              List<Integer> list=new ArrayList<>();
              for(int i=0;i<n;i++){
                  list.add(inputInt());
              }
             // System.out.println(list);
  
                  long ans=Long.MAX_VALUE;
                 long low=1;
                 long high=h;
                 while (low<=high){
                     long mid=low+(high-low)/2;
                     long sum=0;
                     for(int i=0;i<n-1;i++){
                         long diff=(long)list.get(i+1)-list.get(i);
                         sum+=Math.min(mid,diff);
                     }
                     sum+=mid;
                     if(sum<h){
  
                      low=mid+1;
                     }
                     else {
                         ans=Math.min(mid,ans);
                      high=mid-1;
                     }
                 }
                  println(ans+"");
  
  
              //Collections.sort(list);
  
  
  
  
  
          }
  
  
          bw.flush();
          bw.close();
      }
  
      public static boolean checkbool(String s) {
          int i = 0;
          int j = s.length() - 1;
          while (i < j) {
              if (s.charAt(i) != s.charAt(j)) return false;
              i++;
              j--;
          }
          return true;
      }
  
      public static int checker(int a) {
          if (a % 2 == 0) {
              return 1;
          } else {
              byte b;
              do {
                  b = 2;
              } while (a + b != (a ^ b));
  
              return b;
          }
      }
  
      public static boolean checkPrime(int n) {
          if (n != 0 && n != 1) {
              for (int j = 2; j * j <= n; ++j) {
                  if (n % j == 0) {
                      return false;
                  }
              }
  
              return true;
          } else {
              return false;
          }
      }
  
      public static void dfs1(List<List<Integer>> g, boolean[] visited, Stack<Integer> stack, int num) {
          visited[num] = true;
          Iterator var4 = ((List) g.get(num)).iterator();
  
          while (var4.hasNext()) {
              Integer integer = (Integer) var4.next();
              if (!visited[integer]) {
                  dfs1(g, visited, stack, integer);
              }
          }
  
          stack.push(num);
      }
  
      public static void dfs2(List<List<Integer>> g, boolean[] visited, List<Integer> list, int num, int c, int[] raj) {
          visited[num] = true;
          Iterator var6 = ((List) g.get(num)).iterator();
  
          while (var6.hasNext()) {
              Integer integer = (Integer) var6.next();
              if (!visited[integer]) {
                  dfs2(g, visited, list, integer, c, raj);
              }
          }
  
          raj[num] = c;
          list.add(num);
      }
  
      public static int inputInt() throws IOException {
          return sc.nextInt();
      }
  
      public static long inputLong() throws IOException {
          return sc.nextLong();
      }
  
      public static double inputDouble() throws IOException {
          return sc.nextDouble();
      }
  
      public static String inputString() throws IOException {
          return sc.readLine();
      }
  
      public static void print(String a) throws IOException {
          bw.write(a);
      }
  
      public static void printSp(String a) throws IOException {
          bw.write(a + " ");
      }
  
      public static void println(String a) throws IOException {
          bw.write(a + "\n");
      }
  
      public static long getAns(int[] ar, int c, long[][] dp, int i, int sign) {
          if (i < 0) {
              return 1L;
          } else if (c <= 0) {
              return 1L;
          } else {
              dp[i][c] = Math.max(dp[i][c], Math.max((long) ar[i] * getAns(ar, c - 1, dp, i - 1, sign), getAns(ar, c, dp, i - 1, 1)));
              return dp[i][c];
          }
      }
  
      public static long power(long a, long b, long c) {
          long ans;
          for (ans = 1L; b != 0L; b /= 2L) {
              if (b % 2L == 1L) {
                  ans *= a;
                  ans %= c;
              }
  
              a *= a;
              a %= c;
          }
  
          return ans;
      }
  
      public static long power1(long a, long b, long c) {
          long ans;
          for (ans = 1L; b != 0L; b /= 2L) {
              if (b % 2L == 1L) {
                  ans = multiply(ans, a, c);
              }
  
              a = multiply(a, a, c);
          }
  
          return ans;
      }
  
      public static long multiply(long a, long b, long c) {
          long res = 0L;
  
          for (a %= c; b > 0L; b /= 2L) {
              if (b % 2L == 1L) {
                  res = (res + a) % c;
              }
  
              a = (a + a) % c;
          }
  
          return res % c;
      }
  
      public static long totient(long n) {
          long result = n;
  
          for (long i = 2L; i * i <= n; ++i) {
              if (n % i == 0L) {
                  while (n % i == 0L) {
                      n /= i;
                  }
  
                  result -= result / i;
              }
          }
  
          if (n > 1L) {
              result -= result / n;
          }
  
          return result;
      }
  
      public static long gcd(long a, long b) {
          return b == 0L ? a : gcd(b, a % b);
      }
  
      public static boolean[] primes(int n) {
          boolean[] p = new boolean[n + 1];
          p[0] = false;
          p[1] = false;
  
          int i;
          for (i = 2; i <= n; ++i) {
              p[i] = true;
          }
  
          for (i = 2; i * i <= n; ++i) {
              if (p[i]) {
                  for (int j = i * i; j <= n; j += i) {
                      p[j] = false;
                  }
              }
          }
  
          return p;
      }
  
      public String LargestEven(String S) {
          int[] count = new int[10];
  
          int num;
          for (num = 0; num < S.length(); ++num) {
              ++count[S.charAt(num) - 48];
          }
  
          num = -1;
  
          for (int i = 0; i <= 8; i += 2) {
              if (count[i] > 0) {
                  num = i;
                  break;
              }
          }
  
          StringBuilder ans = new StringBuilder();
  
          for (int i = 9; i >= 0; --i) {
              int j;
              if (i != num) {
                  for (j = 1; j <= count[i]; ++j) {
                      ans.append(i);
                  }
              } else {
                  for (j = 1; j <= count[num] - 1; ++j) {
                      ans.append(num);
                  }
              }
          }
  
          if (num != -1 && count[num] > 0) {
              ans.append(num);
          }
  
          return ans.toString();
      }
  
      static {
          bw = new BufferedWriter(new OutputStreamWriter(System.out));
          team1 = 0;
          team2 = 0;
          minkicks = 10;
      }
  
      public static class Score {
          int l;
          String s;
  
          public Score(int l, String s) {
              this.l = l;
              this.s = s;
          }
      }
  
      public static class Ath {
          int r1;
          int r2;
          int r3;
          int r4;
          int r5;
          int index;
  
          public Ath(int r1, int r2, int r3, int r4, int r5, int index) {
              this.r1 = r1;
              this.r2 = r2;
              this.r3 = r3;
              this.r4 = r4;
              this.r5 = r5;
              this.index = index;
          }
      }
  
      static class Reader {
          private final int BUFFER_SIZE = 65536;
          private DataInputStream din;
          private byte[] buffer;
          private int bufferPointer;
          private int bytesRead;
  
          public Reader() {
              this.din = new DataInputStream(System.in);
              this.buffer = new byte[65536];
              this.bufferPointer = this.bytesRead = 0;
          }
  
          public Reader(String file_name) throws IOException {
              this.din = new DataInputStream(new FileInputStream(file_name));
              this.buffer = new byte[65536];
              this.bufferPointer = this.bytesRead = 0;
          }
  
          public String readLine() throws IOException {
              byte[] buf = new byte[64];
  
              int cnt;
              byte c;
              for (cnt = 0; (c = this.read()) != -1 && c != 10; buf[cnt++] = (byte) c) {
              }
  
              return new String(buf, 0, cnt);
          }
  
          public int nextInt() throws IOException {
              int ret = 0;
  
              byte c;
              for (c = this.read(); c <= 32; c = this.read()) {
              }
  
              boolean neg = c == 45;
              if (neg) {
                  c = this.read();
              }
  
              do {
                  ret = ret * 10 + c - 48;
              } while ((c = this.read()) >= 48 && c <= 57);
  
              return neg ? -ret : ret;
          }
  
          public long nextLong() throws IOException {
              long ret = 0L;
  
              byte c;
              for (c = this.read(); c <= 32; c = this.read()) {
              }
  
              boolean neg = c == 45;
              if (neg) {
                  c = this.read();
              }
  
              do {
                  ret = ret * 10L + (long) c - 48L;
              } while ((c = this.read()) >= 48 && c <= 57);
  
              return neg ? -ret : ret;
          }
  
          public double nextDouble() throws IOException {
              double ret = 0.0D;
              double div = 1.0D;
  
              byte c;
              for (c = this.read(); c <= 32; c = this.read()) {
              }
  
              boolean neg = c == 45;
              if (neg) {
                  c = this.read();
              }
  
              do {
                  ret = ret * 10.0D + (double) c - 48.0D;
              } while ((c = this.read()) >= 48 && c <= 57);
  
              if (c == 46) {
                  while ((c = this.read()) >= 48 && c <= 57) {
                      ret += (double) (c - 48) / (div *= 10.0D);
                  }
              }
  
              return neg ? -ret : ret;
          }
  
          private void fillBuffer() throws IOException {
              this.bytesRead = this.din.read(this.buffer, this.bufferPointer = 0, 65536);
              if (this.bytesRead == -1) {
                  this.buffer[0] = -1;
              }
  
          }
  
          private byte read() throws IOException {
              if (this.bufferPointer == this.bytesRead) {
                  this.fillBuffer();
              }
  
              return this.buffer[this.bufferPointer++];
          }
  
          public void close() throws IOException {
              if (this.din != null) {
                  this.din.close();
              }
          }
      }
  }
  