#include<bits/stdc++.h>
using namespace std;
int main(){
  int n,d;
  cin>>n>>d;
  float p=3.14;
  printf("%.2f",p*n*n-p*d*d);
    return 0;
}
/**************************************************************
	Problem: 1338
	User: wangyousi
	Language: C++
	Result: Accepted
	Time:10 ms
	Memory:2072 kb
****************************************************************/