#include<bits/stdc++.h>
using namespace std;
int main(){
	int r1,r2;
	const double PI=3.14;
	double p;
	scanf("%d %d",&r1,&r2);
	p=(r1*r1-r2*r2)*PI;
	printf("%.2f",p);
} 
/**************************************************************
	Problem: 1338
	User: xiaojingxuan
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2076 kb
****************************************************************/