#include <bits/stdc++.h>
#define all(x) (x).begin(), (x).end()
using namespace std;
typedef long long ll;
typedef long double ld;
const int mod = 1e9 + 7;
const int N = 1e6 + 5;

void solve() {
	int n; cin >> n;
	vector<int> a(n), b(n), c(n);
	for (int i = 0; i < n; i++)
		cin >> a[i];
	ll sm = 0;
	ld lo = 1, hi = 1e9;
	int m = -1;
	for (int i = 1; i + 1 < n; i++) {
		if (a[i - 1] > a[i] && a[i] < a[i + 1]) {
			assert(m == -1);
			m = i;
		}
	}
	assert(m != -1);
	for (int it = 0; it < 100; it++) {
		ld mi = (lo + hi) / 2, pref = 0, mn = 0;
		int ok = 0;
		for (int i = 0; i < m; i++) {
			pref += a[i] - mi;
			mn = min(mn, pref);
		}
		pref += a[m] - mi;
		for (int i = m + 1; !ok && i < n; i++) {
			pref += a[i] - mi;
			if (pref >= mn)
				ok = 1;
		}
		if (ok == 1)
			lo = mi;
		else
			hi = mi;
	}
	cout << fixed << setprecision(20) << lo << "\n";
}

int main() {
	ios_base::sync_with_stdio(false); cin.tie(0);
	int t; cin >> t; while (t--) solve();
}