#include<bits/stdc++.h>
using namespace std;
int main(){
	float t,s1,s2,r1,r2;
	cin>>r1>>r2;
	s1=3.14*r1*r1;
	s2=3.14*r2*r2;
	t=s1-s2;
	printf("%.2f",t);
}
/**************************************************************
	Problem: 1338
	User: sucongyi
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2072 kb
****************************************************************/