#include<bits/stdc++.h>
using namespace std;
int main(){
	float r1,r2;
	cin>>r1>>r2;
	printf("%.2f",(3.14*r1*r1)-3.14*r2*r2);
}
/**************************************************************
	Problem: 1338
	User: baizhoudeyueguang
	Language: C++
	Result: Accepted
	Time:16 ms
	Memory:2072 kb
****************************************************************/