/* -*- coding: utf-8 -*-
 *
 * 2648.cc:  No.2648 [Cherry 6th Tune D] 一次元の馬 - yukicoder
 */

#include<cstdio>
#include<algorithm>
 
using namespace std;

/* constant */

const int MAX_N = 200000;

/* global variables */

int as[MAX_N];

/* main */

int main() {
  int tn;
  scanf("%d", &tn);

  while (tn--) {
    int n;
    scanf("%d", &n);
    for (int i = 0; i < n; i++) scanf("%d", as + i);

    int maxc = 0;
    for (int i = 0; i + 1 < n; i++)
      if (as[i] >= as[i + 1]) {
	maxc = max(maxc, as[i] - as[i + 1] + 1);
      }

    printf("%d\n", maxc);
    
  }

  return 0;
}