import java.util.*;
public class Main {
	public static void main(String[] args){
	  Scanner sc = new Scanner(System.in);
      //文字列
      String s =sc.nextLine();
      int c = 0;
      if(s.charAt(0) == '1'){
      	c++;
      }
      if(s.charAt(1) == '1'){
      	c++;
      }
      if(s.charAt(2) == '1'){
        c++;
      }
      
      System.out.print(c);
		
	}
} import java.util.*; util.* java public class Main {
	public static void main(String[] args){
	  Scanner sc = new Scanner(System.in);
      //文字列
      String s =sc.nextLine();
      int c = 0;
      if(s.charAt(0) == '1'){
      	c++;
      }
      if(s.charAt(1) == '1'){
      	c++;
      }
      if(s.charAt(2) == '1'){
        c++;
      }
      
      System.out.print(c);
		
	}
} Main public static void main(String[] args){
	  Scanner sc = new Scanner(System.in);
      //文字列
      String s =sc.nextLine();
      int c = 0;
      if(s.charAt(0) == '1'){
      	c++;
      }
      if(s.charAt(1) == '1'){
      	c++;
      }
      if(s.charAt(2) == '1'){
        c++;
      }
      
      System.out.print(c);
		
	} main {
	  Scanner sc = new Scanner(System.in);
      //文字列
      String s =sc.nextLine();
      int c = 0;
      if(s.charAt(0) == '1'){
      	c++;
      }
      if(s.charAt(1) == '1'){
      	c++;
      }
      if(s.charAt(2) == '1'){
        c++;
      }
      
      System.out.print(c);
		
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String s =sc.nextLine(); s sc.nextLine() sc.nextLine sc int c = 0; c 0 if(s.charAt(0) == '1'){
      	c++;
      } s.charAt(0) == '1' s.charAt(0) s.charAt s 0 '1' {
      	c++;
      } c++ c if(s.charAt(1) == '1'){
      	c++;
      } s.charAt(1) == '1' s.charAt(1) s.charAt s 1 '1' {
      	c++;
      } c++ c if(s.charAt(2) == '1'){
        c++;
      } s.charAt(2) == '1' s.charAt(2) s.charAt s 2 '1' {
        c++;
      } c++ c System.out.print(c) System.out.print System.out System System.out c String[] args args public class Main {
	public static void main(String[] args){
	  Scanner sc = new Scanner(System.in);
      //文字列
      String s =sc.nextLine();
      int c = 0;
      if(s.charAt(0) == '1'){
      	c++;
      }
      if(s.charAt(1) == '1'){
      	c++;
      }
      if(s.charAt(2) == '1'){
        c++;
      }
      
      System.out.print(c);
		
	}
} public class Main {
	public static void main(String[] args){
	  Scanner sc = new Scanner(System.in);
      //文字列
      String s =sc.nextLine();
      int c = 0;
      if(s.charAt(0) == '1'){
      	c++;
      }
      if(s.charAt(1) == '1'){
      	c++;
      }
      if(s.charAt(2) == '1'){
        c++;
      }
      
      System.out.print(c);
		
	}
} Main
import java.util.*;
public class Main {
	public static void main(String[] args){
	  Scanner sc = new Scanner(System.in);
      //文字列
      String s =sc.nextLine();
      int c = 0;
      if(s.charAt(0) == '1'){
      	c++;
      }
      if(s.charAt(1) == '1'){
      	c++;
      }
      if(s.charAt(2) == '1'){
        c++;
      }
      
      System.out.print(c);
		
	}
}
