#include <stdio.h>
#include <iostream>

using namespace std;

int main()
{
	float pi = 3.14152;
	int L, D ;
	freopen("STDIN", "r", stdin);
	cin >> L >> D;
	float r = D /2 ;
	float height = L * 1.7320508075688 / 2;

	float cilinderVolume = pi * r * r * height;
	float other = height* L * 0.5 * pi * D;
float result = cilinderVolume + other;
	freopen("STDOUT", "a", stdout);
	cout << result;
	return 0;
}
