#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll = long long;
using ld = long double;
using mint = modint998244353;

void solve() {
  int N; cin >> N;
  vector<ll> A(N + 1);
  for (int i = 1; i <= N; i++) cin >> A[i];
  ll ans = 0;
  for (int i = 1; i <= N - 1; i++) {
    if (A[i] >= A[i + 1]) {
      ans = max(ans, A[i] - A[i + 1] + 1);
    } 
  }
  cout << ans << endl;
}

int main() {
  int T; cin >> T;
  while (T--) {
    solve();
  }
  return 0;
}