#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
void solve(){
  int r;
  cin>>r;
  cout<<setprecision(10)<<(double)3*sqrt(3)*r*r/4<<endl;
}
int main(){
  int t;
  cin>>t;
  rep(i,t) solve();
}