#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < n; ++i)
typedef long long ll;
using namespace std;

int main() {
    int T;
    cin >> T;
    while (T--) {
        double r;
        cin >> r;

        double ans = 3 * sqrt(3) * r * r / 4;
        printf("%.10f\n", ans);
    }

    return 0;
}