# include<bits/stdc++.h>
using namespace std;
int main(){
	float r1,r2,a;
	cin>>r1>>r2;
	a=r1*3.14*r1-r2*3.14*r2;
	cout<<a<<setprecision(2);




    return 0;
}

/**************************************************************
	Problem: 1338
	User: caiqiaoxi
	Language: C++
	Result: Accepted
	Time:13 ms
	Memory:2072 kb
****************************************************************/