import java.util.*;
public class Main {
  public static void main(String[] args){

    Scanner sc = new Scanner(System.in);
    String s = sc.next();

    String s1 = s.substring(0,1);
    String s2 = s.substring(1,2);
    String s3 = s.substring(2,3);

    int count = 0;

    if (s1.equals("1")) {
      count++;
    }

    if (s2.equals("1")) {
      count++;
    }

    if (s3.equals("1")) {
      count++;
    }

    System.out.println(count);

  }
} import java.util.*; util.* java public class Main {
  public static void main(String[] args){

    Scanner sc = new Scanner(System.in);
    String s = sc.next();

    String s1 = s.substring(0,1);
    String s2 = s.substring(1,2);
    String s3 = s.substring(2,3);

    int count = 0;

    if (s1.equals("1")) {
      count++;
    }

    if (s2.equals("1")) {
      count++;
    }

    if (s3.equals("1")) {
      count++;
    }

    System.out.println(count);

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

    Scanner sc = new Scanner(System.in);
    String s = sc.next();

    String s1 = s.substring(0,1);
    String s2 = s.substring(1,2);
    String s3 = s.substring(2,3);

    int count = 0;

    if (s1.equals("1")) {
      count++;
    }

    if (s2.equals("1")) {
      count++;
    }

    if (s3.equals("1")) {
      count++;
    }

    System.out.println(count);

  } main {

    Scanner sc = new Scanner(System.in);
    String s = sc.next();

    String s1 = s.substring(0,1);
    String s2 = s.substring(1,2);
    String s3 = s.substring(2,3);

    int count = 0;

    if (s1.equals("1")) {
      count++;
    }

    if (s2.equals("1")) {
      count++;
    }

    if (s3.equals("1")) {
      count++;
    }

    System.out.println(count);

  } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String s = sc.next(); s sc.next() sc.next sc String s1 = s.substring(0,1); s1 s.substring(0,1) s.substring s 0 1 String s2 = s.substring(1,2); s2 s.substring(1,2) s.substring s 1 2 String s3 = s.substring(2,3); s3 s.substring(2,3) s.substring s 2 3 int count = 0; count 0 if (s1.equals("1")) {
      count++;
    } s1.equals("1") s1.equals s1 "1" {
      count++;
    } count++ count if (s2.equals("1")) {
      count++;
    } s2.equals("1") s2.equals s2 "1" {
      count++;
    } count++ count if (s3.equals("1")) {
      count++;
    } s3.equals("1") s3.equals s3 "1" {
      count++;
    } count++ count System.out.println(count) System.out.println System.out System System.out count String[] args args public class Main {
  public static void main(String[] args){

    Scanner sc = new Scanner(System.in);
    String s = sc.next();

    String s1 = s.substring(0,1);
    String s2 = s.substring(1,2);
    String s3 = s.substring(2,3);

    int count = 0;

    if (s1.equals("1")) {
      count++;
    }

    if (s2.equals("1")) {
      count++;
    }

    if (s3.equals("1")) {
      count++;
    }

    System.out.println(count);

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

    Scanner sc = new Scanner(System.in);
    String s = sc.next();

    String s1 = s.substring(0,1);
    String s2 = s.substring(1,2);
    String s3 = s.substring(2,3);

    int count = 0;

    if (s1.equals("1")) {
      count++;
    }

    if (s2.equals("1")) {
      count++;
    }

    if (s3.equals("1")) {
      count++;
    }

    System.out.println(count);

  }
} Main
import java.util.*;
public class Main {
  public static void main(String[] args){

    Scanner sc = new Scanner(System.in);
    String s = sc.next();

    String s1 = s.substring(0,1);
    String s2 = s.substring(1,2);
    String s3 = s.substring(2,3);

    int count = 0;

    if (s1.equals("1")) {
      count++;
    }

    if (s2.equals("1")) {
      count++;
    }

    if (s3.equals("1")) {
      count++;
    }

    System.out.println(count);

  }
}