#include<bits/stdc++.h>
using namespace std;
int main(){
	int r1,r2;
	cin>>r1>>r2;
	printf("%.2f",(r1*r1-r2*r2)*3.14);
}
 
/**************************************************************
	Problem: 1338
	User: lvrenxiang
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2072 kb
****************************************************************/