#include<bits/stdc++.h>
using namespace std;

int main(){
	int r1,r2;
	double s,pi = 3.14;
	cin>>r1>>r2;
	s = pi * r1 * r1 - pi * r2 * r2;
	cout<<fixed<<setprecision(2)<<s<<endl; 
	 
    return 0;
}

/**************************************************************
	Problem: 1338
	User: admin
	Language: C++
	Result: Accepted
	Time:9 ms
	Memory:2072 kb
****************************************************************/