#include <bits/stdc++.h>
using namespace std;
int main(){
  cout << fixed << setprecision(20);
  int t;
  cin >> t;
  for (int i = 0; i < t; i++){
    double r;
    cin >> r;
    cout << 3 * sqrt(3) / 4 * r * r << endl;
  }
}