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#include <bits/stdc++.h>
using namespace std;
typedef long long LL;

LL C2(LL n) {
    if (n < 2) return 0;
    return n * (n - 1) / 2;
}

LL C3(LL n) {
    if (n < 3) return 0;
    return n * (n - 1) * (n - 2) / 6;
}

bool check(const vector<LL>& s, LL m) {
    int n = s.size();
    LL p_prev = 0;
    for (int j = 1; j <= n; ++j) {
        LL low = p_prev;
        LL high = m;
        LL best_p = -1;
        while (low <= high) {
            LL mid = low + (high - low) / 2;
            LL val = C3(mid) + C2(mid) * (m - mid);
            if (val >= s[j - 1]) {
                best_p = mid;
                high = mid - 1;
            } else {
                low = mid + 1;
            }
        }
        if (best_p == -1) return false;
        p_prev = best_p;
    }
    return p_prev <= m;
}

void solve(){
    int n;
    cin >> n;
    vector<LL> a(n);
    for (int i = 0; i < n; ++i) {
        cin >> a[i];
    }

    vector<LL> s(n);
    s[0] = a[0];
    for (int j = 1; j < n; ++j) {
        s[j] = s[j - 1] + a[j];
    }

    LL low = 0;
    LL high = 1e6;
    LL ans = -1;
    while (low <= high) {
        LL mid = low + (high - low) / 2;
        if (check(s, mid)) {
            ans = mid;
            high = mid - 1;
        } else {
            low = mid + 1;
        }
    }
    cout << ans << '\n';
}

int main() {
    cin.tie(0)->sync_with_stdio(0);

    int t;
    cin >> t;
    while(t--)solve();

    return 0;
}