package com.company;

import java.util.Scanner;

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

        int number = Integer.parseInt(scanner.nextLine());

        int sum = 0;
        while (number > 0) {
            int lastDigit = number % 10;
            number /= 10;

            sum += lastDigit;
        }

        System.out.println(sum);
    }
}