#define _USE_MATH_DEFINES
#include <iostream>
#include <cmath>

using namespace std;
int main()
{
    int ans;
    int a;
    double cons;

    cin >> a;

    cons = (pow(M_PI, 2.0))/6;
    /*ans = (-1/3)*pow(M_PI, 4.0)*pow(1/sin(M_PI/a), 2.0)*(2pow(1/tan(M_PI/a), 2.0)+pow(1/sin(M_PI/a), 2.0));*/
    ans = (1./a)*pow(cons, a);
    cout << ans << endl;
}