import java.util.Arrays;
import java.util.List;
import java.util.Scanner;

public class App {
    public static void main(String[] args) throws Exception {
        // yukicorder No.9011 数字を全て足そう（数字だけ）

        Scanner scanner = new Scanner(System.in);
        String s = scanner.nextLine();
        scanner.close();

        List<String> sList = Arrays.asList(s.split(""));
        int total = sList.stream().mapToInt(Integer::parseInt).sum();

        System.out.println(total);
    }
}