#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);
	return 0;
}
/**************************************************************
	Problem: 1338
	User: panyuchen
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/