#include <bits/stdc++.h>
using namespace std;

int main()
{
	int t;
	cin >> t;
	for( int i = 0; i < t; i++ ) {
		double r;
		cin >> r;
		double a = r * r * sin( M_PI * 2 / 3 ) * 3 / 2;
		cout << fixed << setprecision(12) << a << endl;
	}
}