#include<iostream>
#include<cmath>
#include<cassert>
#define rep(i,n) for(i=0;i<(int)(n);i++)
using namespace std;
typedef long long ll;
typedef unsigned long long ull;

int t,r;

int main(){
    scanf("%d",&t);
    while(t--){
        scanf("%d",&r);
        printf("%.5f\n",3.0*sqrt(3)*r*r/4);
    }
    return 0;
}