import java.util.*;

public class Main {
    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);

        for(int i = 0; i < 1; i = 0) {
          String line = sc.nextLine();
          String[] l = line.split("");

          int len = l.length;
          int ans = 0;
          for(int j = 0; j < len; j++) {
            ans += Integer.parseInt(l[j]);
          }

          if(ans == 0) {
            break;
          }

          System.out.println(ans);
        }
    }
}
/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