#include<bits/stdc++.h>
using namespace std;
int main(){
	int r1,r2;
	float s;
	scanf("%d %d",&r1,&r2);
	s=r1*r1*3.14-r2*r2*3.14;
	printf("%.2f",s); 
	return 0;
}

/**************************************************************
	Problem: 1338
	User: fuhoubin
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2076 kb
****************************************************************/