#include<bits/stdc++.h>
using namespace std;
int main() {
	float r1,r2,i=0,j=0,s; 
	cin>>r1>>r2;
	i=r1*r1*3.14;
	j=r2*r2*3.14;
	s=i-j;
	printf("%.2f",s);
	 
}

/**************************************************************
	Problem: 1338
	User: chenjunlin
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/