#include <bits/stdc++.h>
using namespace std;
#define int long long
#define nl "\n"
#define pb push_back
#define mk make_pair
#define pii pair<int, int>
#define vi vector<int>
#define all(x) (x).begin(), (x).end()
#define umap unordered_map
#define uset unordered_set
#define MOD 1000000007
#define exp 1e9
#define sz(x) (int((x).size()))
#define forn(i, a, b) for (long long i = a; i < b; i++)
#define Yes cout << "Yes" << endl
#define No cout << "No" << endl

void solve()
{
    int n;
    cin >> n;

    vi a(n);
    for (auto &i : a)
        cin >> i;

    int ans = 0;

    bool isSorted = true;
    for (int i = 1; i < n; i++)
    {
        if (a[i] <= a[i - 1])
        {
            isSorted = false;
            break;
        }
    }

    if (isSorted)
    {
        cout << 0 << endl;
    }
    else
    {
        int maxDiff = INT_MIN;
        for (int i = 1; i < n; i++)
        {
            int diff = abs(a[i] - a[i - 1]);
            maxDiff = max(maxDiff, diff);
        }

        cout << maxDiff + 1 << endl;
    }
}

int32_t main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    int tc = 1;
    cin >> tc;
    // cout << tc;
    while (tc--)
    {
        solve();
    }
}