import java.util.Scanner;

public class SumOfDigits {
	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		int n;
		System.out.print("Enter a positive integer: ");
		n = in.nextInt();
		if (n <= 0)
			System.out.println("Integer you've entered is nonpositive.");
		else {
			int sum = 0;
			// algorithm step by step
			// base: sum = 0, n = 123
			// step1: n % 10 = 3, n / 10 = 12
			// 		  sum = 3, n = 12
			// step2: n % 10 = 2, n / 10 = 1
			// 		  sum = 5, n = 1
			// step3: n % 10 = 1, n / 10 = 0
			// 		  sum = 6, n = 0
			// stop: (n != 0) is false
			while (n != 0) {
				// add last digit to the sum
				sum += n % 10;
				// cut last digit
				n /= 10;
			}
			System.out.println("Sum: " + sum);
		}
	}
}