import java.util.Scanner;
public class Main {

    public static int f(int n){
        if (n==1)
            return 1;
        else
            return f(n-1)+2;
    }

    public static void main(String[] args) {
        int n;
        n = new Scanner(System.in).nextInt();
        System.out.println(f(n));
    }
}