import java.util.*;
public class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        sc.close();
        double s = Math.PI * Math.PI / 6;
        s = Math.pow(s , n) * 1.0 / n;
        System.out.println((int) s);
    }
}