#include <iostream>
#include <algorithm>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <numeric>
#include <bitset>
#include <cmath>

static const int MOD = 1000000007;
using ll = long long;
using uint = unsigned;
using ull = unsigned long long;
using namespace std;

template<class T> constexpr T INF = ::numeric_limits<T>::max() / 32 * 15 + 208;

int main() {
    int t;
    cin >> t;
    while(t--){
        int r;
        cin >> r;
        printf("%.10lf\n", 3.0/4*sqrt(3)*r*r);
    }
    return 0;
}