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

public class App {
    public static void main(String[] args) throws Exception {
        // System.out.println("Hello, World!");
        // ■標準入力
        // Scannerクラス
        Scanner scanner = new Scanner(System.in);

        // nextLineメソッド
        String s = scanner.nextLine();

        String[] sArray = s.split("");
        List<String> sList = Arrays.asList(sArray);
        List<Integer> sIntList = new ArrayList<>();
        sList.stream().forEach(h -> {
            Integer intS = Integer.valueOf(h);
            sIntList.add(intS);
        });

        int total = sIntList.stream().mapToInt(val -> val).sum();

        System.out.println(total);
        scanner.close();
    }
}