Untitled

import java.util.Scanner;

public class P1 {
	public static int Sol(int n) {
		int sum = 0;

		for (int i = 2; i <= n; i += 2) {
			if (n % i == 0) {
				sum += i;

			}
		}
		return sum;
	}

//	6 = 1, 2, 3, 6

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		int n = sc.nextInt();

		System.out.println(Sol(n));
//		Sol(n);
	}
}