#include <iostream>
#include <iomanip>
using namespace std;
int main(){
    double rt = 0.0;
    double ru = 0.0;	
	double p =3.1415926;
	cin>>rt;
	cin>>ru;
	double s=rt*rt*p;
	double a=ru*ru*p;
	double o = s-a; 
    cout << fixed << setprecision(2)<<o<<endl;
    
}