#include <bits/stdc++.h>
using namespace std;
int main(){
    float a,x,y;
    cin>>x>>y;
    a=x*x*3.14-y*y*3.14;
    printf("%.2f",a);
}
/**************************************************************
	Problem: 1338
	User: yangjunwen
	Language: C++
	Result: Accepted
	Time:6 ms
	Memory:2072 kb
****************************************************************/