#include<bits/stdc++.h>
using namespace std;
int main(){
int n,b;
float m;
cin>>n>>b;
m=n*n*3.14-b*b*3.14;
printf("%.2f",m); 
}

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