#ifndef LOCAL
#include <bits/stdc++.h>

using namespace std;

#define debug(...) (void(0))
#else
#include "algo/debug.h"
#endif

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

int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    int tt = 1;
    std::cin >> tt;
    while (tt--) {
        solve();
    }
}