import java.util.Scanner;


public class prog {
    public static void main (String[] args) throws java.lang.Exception
    {
        Scanner scanner = new Scanner(System.in);
        int n = Integer.parseInt(scanner.nextLine());
        int flairs = 15;
        for (int i = 1; i <= n; i++) {
            if(flairs-i < 15){
                flairs+=i;
            } else {
                flairs-=i;
            }
        }
        System.out.println(flairs);
        scanner.close();
    }
}