import java.util.*;

public class Main {
	public static void main(String args[]) {
		Scanner sc = new Scanner(System.in);
		while (sc.hasNext()) {
			long N = sc.nextLong();
			if (N == 0)
				break;

			long sum = 0;
			long ans = 0, times, R, L = 1;
			long count = 0;

			while (L <= N) {
	            times = N / L;
	            R = N / times;
	            ans += times * ((L + R) * (R - L + 1) / 2);
	            L = R + 1;
	            count++;
	        }
			System.out.println(ans - 1);
		}
	}
}