#include<bits/stdc++.h>
using namespace std;
int main(){
   int r1,r2;
   cin>>r1>>r2;
   printf("%.2f",3.14*r1*r1-3.14*r2*r2);
}//1674
/**************************************************************
	Problem: 1338
	User: linmiaoling
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/