#include<bits/stdc++.h>
using namespace std;
int main(){
   int r1,r2;
   float pi=3.14,a,b,s;
   cin>>r1>>r2;
   a=r1*r1*pi*1.0;
   b=r2*r2*pi*1.0;
   s=a-b;
   printf("%.2f",s);
}
/**************************************************************
	Problem: 1338
	User: toughuatao1
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/