#include<bits/stdc++.h>
using namespace std;
int r1,r2;
const float PI=3.14;
double s1,s2;
int main(){
	cin>>r1>>r2;
	s1=r1*r1*PI;
	s2=r2*r2*PI;
	cout<<fixed<<setprecision(2)<<s1-s2;
	return 0;
}

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