#include <iostream>
#include <math.h>
#include <stdio.h>
using namespace std;
double MaxArea(int r)
{
	double area = (3.0 * r *sqrt(3.0)*r) / 4.0;
	return area;
}
int main()
{
	int t,i;
	int r;
	cin >> t;
	for (i = 0; i < t; i++) {
		cin >> r;
		printf("%.15lf\n", MaxArea(r));
	}
	return 0;
}