import java.util.*;

public class Main{
  public static void main(String args[]){
    Scanner sc = new Scanner(System.in);
    
    String s = sc.nextLine();
    int count = 0;
    if(String.valueOf(s.charAt(0)).equals("1")){
      count+=1;
    }
    if(String.valueOf(s.charAt(1)).equals("1")){
      count+=1;
    }
    if(String.valueOf(s.charAt(2)).equals("1")){
      count+=1;
    }
    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.nextLine();
    int count = 0;
    if(String.valueOf(s.charAt(0)).equals("1")){
      count+=1;
    }
    if(String.valueOf(s.charAt(1)).equals("1")){
      count+=1;
    }
    if(String.valueOf(s.charAt(2)).equals("1")){
      count+=1;
    }
    System.out.println(count);
  }
} Main public static void main(String args[]){
    Scanner sc = new Scanner(System.in);
    
    String s = sc.nextLine();
    int count = 0;
    if(String.valueOf(s.charAt(0)).equals("1")){
      count+=1;
    }
    if(String.valueOf(s.charAt(1)).equals("1")){
      count+=1;
    }
    if(String.valueOf(s.charAt(2)).equals("1")){
      count+=1;
    }
    System.out.println(count);
  } main {
    Scanner sc = new Scanner(System.in);
    
    String s = sc.nextLine();
    int count = 0;
    if(String.valueOf(s.charAt(0)).equals("1")){
      count+=1;
    }
    if(String.valueOf(s.charAt(1)).equals("1")){
      count+=1;
    }
    if(String.valueOf(s.charAt(2)).equals("1")){
      count+=1;
    }
    System.out.println(count);
  } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String s = sc.nextLine(); s sc.nextLine() sc.nextLine sc int count = 0; count 0 if(String.valueOf(s.charAt(0)).equals("1")){
      count+=1;
    } String.valueOf(s.charAt(0)).equals("1") String.valueOf(s.charAt(0)).equals String.valueOf(s.charAt(0)) String.valueOf String s.charAt(0) s.charAt s 0 "1" {
      count+=1;
    } count+=1 count 1 if(String.valueOf(s.charAt(1)).equals("1")){
      count+=1;
    } String.valueOf(s.charAt(1)).equals("1") String.valueOf(s.charAt(1)).equals String.valueOf(s.charAt(1)) String.valueOf String s.charAt(1) s.charAt s 1 "1" {
      count+=1;
    } count+=1 count 1 if(String.valueOf(s.charAt(2)).equals("1")){
      count+=1;
    } String.valueOf(s.charAt(2)).equals("1") String.valueOf(s.charAt(2)).equals String.valueOf(s.charAt(2)) String.valueOf String s.charAt(2) s.charAt s 2 "1" {
      count+=1;
    } count+=1 count 1 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.nextLine();
    int count = 0;
    if(String.valueOf(s.charAt(0)).equals("1")){
      count+=1;
    }
    if(String.valueOf(s.charAt(1)).equals("1")){
      count+=1;
    }
    if(String.valueOf(s.charAt(2)).equals("1")){
      count+=1;
    }
    System.out.println(count);
  }
} public class Main{
  public static void main(String args[]){
    Scanner sc = new Scanner(System.in);
    
    String s = sc.nextLine();
    int count = 0;
    if(String.valueOf(s.charAt(0)).equals("1")){
      count+=1;
    }
    if(String.valueOf(s.charAt(1)).equals("1")){
      count+=1;
    }
    if(String.valueOf(s.charAt(2)).equals("1")){
      count+=1;
    }
    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.nextLine();
    int count = 0;
    if(String.valueOf(s.charAt(0)).equals("1")){
      count+=1;
    }
    if(String.valueOf(s.charAt(1)).equals("1")){
      count+=1;
    }
    if(String.valueOf(s.charAt(2)).equals("1")){
      count+=1;
    }
    System.out.println(count);
  }
}