#include<bits/stdc++.h>
using namespace std;
int main(){
    float t,s1,s2,r1,r2;
    cin>>r1>>r2;
    s1=3.14*r1*r1;
    s2=3.14*r2*r2;
    t=s1-s2;
    printf("%.2f",t);
}
/**************************************************************
	Problem: 1338
	User: xuezihong1
	Language: C++
	Result: Accepted
	Time:17 ms
	Memory:2072 kb
****************************************************************/