using static System.Math;
using System;

public class Hello
{
    static void Main()
    {
        var T = int.Parse(Console.ReadLine().Trim());
        while (T-- > 0)
        {
            var n = int.Parse(Console.ReadLine().Trim());
            string[] line = Console.ReadLine().Trim().Split(' ');
            var a = Array.ConvertAll(line, int.Parse);
            getAns(n, a);
        }
    }
    static void getAns(int n, int[] a)
    {
        var ans = 0;
        for (int i = 0; i < n - 1; i++)
        {
            if (a[i] < a[i + 1]) continue;
            var d = a[i] - a[i + 1];
            ans = Max(ans, d + 1);
        }
        Console.WriteLine(ans);
    }
}