#include<bits/stdc++.h>
using namespace std;
int main ()
{
double A, n, R, Square_of_R;
cin >> R;
Square_of_R = pow(R,2);
n = 3.14159;
A = n * Square_of_R;
cout << "A=" << fixed << setprecision(4) << A << endl;
//printf("A=%.4lf", A);
return 0;
}