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 static java.lang.Math.*;
  
  public class C {
  
  	public Object solve () {
  		sc.nextInt();
  		H = sc.nextLong();
  		A = sc.nextLongs();
  
  		long p = 0, q = LINF, m;
  		while (q - p > 1) {
  			m = (p + q) / 2;
  			if (calc(m))
  				q = m;
  			else
  				p = m;
  		}
  
  		return q;
  	}
  
  	boolean calc (long m) {
  		int N = A.length;
  
  		long Z = m;
  		for (int i : rep(N-1))
  			Z += min(A[i+1] - A[i], m);
  
  		return Z >= H;
  	}
  
  	long [] A;
  	long H;
  
  	private static final int CONTEST_TYPE = 2;
  
  	private static void init () {
  	}
  
  	private static final long LINF = (long) 1e18 + 10;
  	private static int [] rep (int N) { return rep(0, N); }
  	private static int [] rep (int S, int T) { if (S >= T) return new int [0]; int [] res = new int [T-S]; for (int i = S; i < T; ++i) res[i-S] = i; return res; }
  	//////////////////////////////////////////////////////////////////////////////////// OFF
  	private static IOUtils.MyScanner sc = new IOUtils.MyScanner();
  	private static class IOUtils {
  		public static class MyScanner {
  			public String next () { newLine(); return line[index++]; }
  			public int nextInt () { return Integer.parseInt(next()); }
  			public long nextLong () { return Long.parseLong(next()); }
  			public String nextLine () { line = null; return readLine(); }
  			public String [] nextStrings () { return split(nextLine()); }
  			public long [] nextLongs () {
  				String [] S = nextStrings(); int N = S.length;
  				long [] res = new long [N];
  				for (int i = 0; i < N; ++i)
  					res[i] = Long.parseLong(S[i]);
  				return res;
  			}
  			//////////////////////////////////////////////
  			private boolean eol () { return index == line.length; }
  			private String readLine () {
  				try {
  					int b;
  					StringBuilder res = new StringBuilder();
  					while ((b = System.in.read()) < ' ')
  						continue;
  					res.append((char)b);
  					while ((b = System.in.read()) >= ' ')
  						res.append((char)b);
  					return res.toString();
  				} catch (Exception e) {
  					throw new Error (e);
  				}
  			}
  			private MyScanner () {
  				try {
  					while (System.in.available() == 0)
  						Thread.sleep(1);
  					start();
  				} catch (Exception e) {
  					throw new Error(e);
  				}
  			}
  			private String [] line;
  			private int index;
  			private void newLine () {
  				if (line == null || eol()) {
  					line = split(readLine());
  					index = 0;
  				}
  			}
  			private String [] split (String s) { return s.length() > 0 ? s.split(" ") : new String [0]; }
  		}
  		private static String build (Object o, Object ... A) { return buildDelim(" ", o, A); }
  		private static String buildDelim (String delim, Object o, Object ... A) {
  			java.util.List<String> str = new java.util.ArrayList<>();
  			append(str, o);
  			for (Object p : A)
  				append(str, p);
  			return String.join(delim, str.toArray(new String [0]));
  		}
  		//////////////////////////////////////////////////////////////////////////////////
  		private static java.text.DecimalFormat formatter = new java.text.DecimalFormat("#.#########");
  		private static void start () { if (t == 0) t = millis(); }
  		private static void append (java.util.function.Consumer<Object> f, java.util.function.Consumer<Object> g, Object o) {
  			if (o.getClass().isArray()) {
  				int len = java.lang.reflect.Array.getLength(o);
  				for (int i = 0; i < len; ++i)
  					f.accept(java.lang.reflect.Array.get(o, i));
  			}
  			else if (o instanceof Iterable<?>)
  				((Iterable<?>)o).forEach(f::accept);
  			else
  				g.accept(o instanceof Double ? formatter.format(o) : o);
  		}
  		private static void append (java.util.List<String> str, Object o) {
  			append(x -> append(str, x), x -> str.add(x.toString()), o);
  		}
  		private static java.io.PrintWriter pw = new java.io.PrintWriter(System.out);
  		private static void flush () { pw.flush(); System.out.flush(); }
  		private static void print (Object o, Object ... A) {
  			String res = build(o, A);
  			if (DEBUG == 2)
  				err(res, '(', time(), ')');
  			if (res.length() > 0)
  				pw.println(res);
  			if (DEBUG == 1)
  				flush();
  		}
  		private static void err (Object o, Object ... A) { System.err.println(build(o, A)); }
  		private static int DEBUG;
  		private static void exit () {
  			String end = "------------------" + System.lineSeparator() + time();
  			switch(DEBUG) {
  			case 1: print(end); break;
  			case 2: err(end); break;
  			}
  			IOUtils.pw.close();
  			System.out.flush();
  			System.exit(0);
  		}
  		private static long t;
  		private static long millis () { return System.currentTimeMillis(); }
  		private static String time () { return "Time: " + (millis() - t) / 1000.0; }
  		private static void run (int N) {
  			try { DEBUG = Integer.parseInt(System.getProperties().get("DEBUG").toString()); }
  			catch (Throwable t) {}
  
  			for (int n = 1; n <= N; ++n) {
  				Object res = new C().solve();
  				if (res != null) {
  					@SuppressWarnings("all")
  					Object o = CONTEST_TYPE == 0 ? "Case #" + n + ": " + build(res) : res;
  					print(o);
  				}
  			}
  			exit();
  		}
  	}
  	////////////////////////////////////////////////////////////////////////////////////
  	public static void main (String[] args) {
  		@SuppressWarnings("all")
  		int N = CONTEST_TYPE == 1 ? 1 : sc.nextInt();
  		init();
  		IOUtils.run(N);
  	}
  }
  