SumDigits

import java.util.Scanner;

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

        int num = scanner.nextInt();
        int num1 = num / 1000 % 10;
        int num2 = num / 100 % 10;
        int num3 = num / 10 % 10;
        int num4 = num % 10;
        int sum = num1 + num2 + num3 + num4;
        System.out.println(sum);

    }
}