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

void solve() {
    int n;
    cin >> n;
    vector<int> a(n);
    for (int &x : a) {
        cin >> x;
    }
    int p;
    for (int i = 0; i < n; i++) {
        if (i == n - 1 || a[i] < a[i + 1]) {
            p = i;
            break;
        }
    }
    double l = 0, r = 1e9;
    for (int _ = 0; _ < 100; _++) {
        double mid = (l + r) / 2;
        double mx = -1e18, sum = 0;
        for (int i = p; i >= 0; i--) {
            sum += a[i] - mid;
            if (i < p) {
                mx = max(mx, sum);
            }
        }
        sum = 0;
        double mx2 = -1e18;
        for (int i = p + 1; i < n; i++) {
            sum += a[i] - mid;
            mx2 = max(mx2, sum);
        }
        double ans = mx + mx2;
        if (ans > 0) {
            l = mid;
        } else {
            r = mid;
        }
    }
    cout << l << "\n";
}

int main() {
    ios::sync_with_stdio(0), cin.tie(0);
    int T;
    cin >> T;
    cout << fixed << setprecision(9);
    while (T--) {
        solve();
    }
    return 0;
}