#include <bits/stdc++.h>
using namespace std;
int main() {
	float k,m,j;
	int a,s;
	cin>>a>>s;
	k=a*a*3.14;
	m=3.14*s*s;
	j=k-m;
	printf("%.2f",j);
}
/**************************************************************
	Problem: 1338
	User: tonghuawei
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/