import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		try (Scanner sc = new Scanner(System.in)) {
			int N = sc.nextInt();
			int sum = 0;
			for (int i = 2;i <= N;++ i) {
				while(N % i == 0) {
					sum += i;
					N /= i;
				}
			}
			System.out.println(sum);
		}
	}
}