#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
const int inf = 1e17 + 1;
#define FL(i, a, n) for (int i = a; i < n; i++)
#define FR(i, a, n) for (int i = a; i >= n; i--)
void solve()
{
    int n;
    cin >> n;
    int l = -1, r = 10;
    vi a(n);
    forn(0, n) cin >> a[i];
    while (r > l + 1)
    {
        int mid = (l + r) / 2;
        vi v(n);
        forn(0, n) v[i] = a[i] + mid * (i + 1);
        bool f = 1;
        forn(1, n)
        {
            if (v[i] <= v[i - 1])
            {
                f = 0;
                break;
            }
        }
        // cout<<f<<" "<<mid<<"-> ";
        // forn(0,n)cout<<v[i]<<" ";
        // nl;
        if (f)
        {
            r = mid;
        }
        else
        {
            l = mid;
        }
    }
    cout << r;
}
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;
}