#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
#define int long long int
template <typename T>
using ordered_set = tree<T, null_type, less_equal<T>, rb_tree_tag, tree_order_statistics_node_update>;
#define ld long double
#define nl cout << "\n";
#define getunique(v) {sort(v.begin(), v.end()); v.erase(unique(v.begin(), v.end()), v.end());}
#define forn(a, b) for (int i = a; i < b; i++)
#define __builtin_popcountll __builtin_popcountll
#define __builtin_clzll __builtin_clzll
#define __builtin_ctzll __builtin_ctzll
#define yesno(b) cout << ((b)? "YES" : "NO");
#define pii pair<int, int>
#define mp(a, b) make_pair(a, b)
#define pb push_back
#define all(a) a.begin(), a.end()
#define vi vector<int>
#define hhh cout << "here" << endl;
#define mod1 1000000007
#define mod2 998244353
void solve()
{
    int n;
    cin >> n;
    
    vector<int> v(n);
    for(int& x : v) cin >> x;

    int l = 0, r = 1e10, mid, ans = 1e10;
    while(l <= r) {
        mid = (l + r) / 2;

        vector<int> temp(n, 0);
        for(int i = 0 ; i < n ; i++) {
            temp[i] = v[i] + ((i + 1) * mid);
        }
        // cout << mid << "   "; for(int x : temp) cout << x << " "; cout << endl;

        bool flag = true;
        for(int i = 1 ; i < n ; i++) if(temp[i] <= temp[i - 1]) flag = false;

        if(flag) {
            ans = mid;
            r = mid - 1;
        }
        else {
            l = mid + 1;
        }
    }
    cout << ans;
}
signed main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    // freopen("input.txt", "r", stdin);
    // freopen("output.txt", "w", stdout);
    int t = 1;
    cin >> t;
    while (t--)
    {
        solve();
        nl;
    }
    return 0;
}