#include<bits/stdc++.h>
using namespace std;
int main(){
    float r1,r2,a;
    cin>>r1>>r2;
    a=r1*3.14*r1-r2*3.14*r2;
    cout<<a<<setprecision(2);
    return 0;
}
/**************************************************************
	Problem: 1338
	User: chenmingyu
	Language: C++
	Result: Accepted
	Time:20 ms
	Memory:2072 kb
****************************************************************/