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#include <bits/stdc++.h>
using namespace std;
#define REP(i,a,b) for (int i = (a); i <= (b); ++i)
#define REPD(i,a,b) for (int i = (a); i >= (b); --i)
#define FORI(i,n) REP(i,1,n)
#define FOR(i,n) REP(i,0,int(n)-1)
#define mp make_pair
#define pb push_back
#define pii pair<int,int>
#define vi vector<int>
#define ll long long
#define SZ(x) int((x).size())
#define DBG(v) cerr << #v << " = " << (v) << endl;
#define FOREACH(i,t) for (typeof(t.begin()) i=t.begin(); i!=t.end(); i++)
#define fi first
#define se second

const int N = 400200;

int n;
int a[N];
ll b[N], c[N];

bool ok(int m) {
	FOR(k,m) b[k] = 1LL*k*(m-1-k);
	int k = 0;
	FOR(i,n) c[i] = a[i];
	FOR(i,n) {
		while (k<m && c[i] > 0) {
			c[i] -= b[k];
			k++;
		}
		if (c[i] > 0 && k == m) return false;
	}
	return true;
}

void test() {
	scanf("%d", &n);
	FOR(i,n) scanf("%d", &a[i]);
	int lo = 2, hi = N;
	while (lo+1 < hi) {
		int mi = (lo+hi) / 2;
		if (ok(mi)) hi = mi;
		else lo = mi;
	}
	printf("%d\n", hi);
}

int main() {
	int tt;
	scanf("%d", &tt);
	FOR(i,tt) test();
	return 0;
}