

    





import java.util.*;

public class Main {
  public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);
    String s = scan.next();
    char[] c = s.toCharArray();
    int ans = 0;
    for (char ch: c) {
      if (ch == '1') {
        ans++;
      }
    }
    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