#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);
} 
/**************************************************************
	Problem: 1338
	User: linzihang
	Language: C++
	Result: Accepted
	Time:9 ms
	Memory:2072 kb
****************************************************************/