#include<bits/stdc++.h>
using namespace std;
int main(){

	float r,r2,s1,s,ss;
	const float pi=3.14;
	cin>>r>>r2;
	s1=pi*r2*r2;
	s=pi*r*r;
	ss=s-s1;
	printf("%.2f",ss);
	return 0;
}


/**************************************************************
	Problem: 1338
	User: tangkaixuan
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/