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

	float r1,r2,x;
	cin>>r1>>r2;
	x=(r1*r1-r2*r2)*3.14;
	printf("%.2f",x);


	return 0;
}

/**************************************************************
	Problem: 1338
	User: zhuangsongyu
	Language: C++
	Result: Accepted
	Time:12 ms
	Memory:2072 kb
****************************************************************/