#include <iostream>
#include <iomanip>
#include <cmath>
using namespace std;
int main(){
    int t;cin>>t;
    for(int i = 0; t > i; i++){
        int x;cin>>x;
        cout << fixed << setprecision(10) << (double)x*x/2*sin((double)2*M_PI/3)*3 << endl;
    }
}