#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000001

int main(){
	int t;
	cin>>t;
	rep(_,t){
	
	double r;
	cin>>r;
	
	double ans = 3.0 * sqrt(3.0) / 4.0;
	ans *= r;
	ans *= r;
	
	cout<<fixed<<setprecision(10)<<ans<<endl;
	}
	
	return 0;
}