import java.util.Scanner;

public class Main {

    public static void main(String[] args) {

                Scanner scan = new Scanner(System.in);
                String[] a = scan.nextLine().split("");

                int count = 0;
                if("1".equals(a[0]))
                    count++;

                if("1".equals(a[1]))
                    count++;
                if("1".equals(a[2]))
                    count++;
                System.out.print(count);

            }
}

/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz