#include<bits/stdc++.h>
using namespace std;
int main(){
    int r1,r2;
    cin>>r1>>r2;
    printf("%.2f",(r1*r1-r2*r2)*3.14);
    return 0;
}
/**************************************************************
	Problem: 1338
	User: panjinyan
	Language: C++
	Result: Accepted
	Time:33 ms
	Memory:2072 kb
****************************************************************/