import java.util.*;


public class Main {
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
      String po[]=sc.nextLine().split("",0);
      int count=0;
      for(int i=0;i<3;i++){
      if(po[i].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 po[]=sc.nextLine().split("",0);
      int count=0;
      for(int i=0;i<3;i++){
      if(po[i].equals("1"))count++;
      }
      System.out.println(count);
    }
} Main public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
      String po[]=sc.nextLine().split("",0);
      int count=0;
      for(int i=0;i<3;i++){
      if(po[i].equals("1"))count++;
      }
      System.out.println(count);
    } main {
        Scanner sc=new Scanner(System.in);
      String po[]=sc.nextLine().split("",0);
      int count=0;
      for(int i=0;i<3;i++){
      if(po[i].equals("1"))count++;
      }
      System.out.println(count);
    } Scanner sc=new Scanner(System.in); sc new Scanner(System.in) String po[]=sc.nextLine().split("",0); po sc.nextLine().split("",0) sc.nextLine().split sc.nextLine() sc.nextLine sc "" 0 int count=0; count 0 for(int i=0;i<3;i++){
      if(po[i].equals("1"))count++;
      } int i=0; int i=0; i 0 i<3 i 3 i++ i++ i {
      if(po[i].equals("1"))count++;
      } {
      if(po[i].equals("1"))count++;
      } if(po[i].equals("1"))count++; po[i].equals("1") po[i].equals po[i] po i "1" 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 po[]=sc.nextLine().split("",0);
      int count=0;
      for(int i=0;i<3;i++){
      if(po[i].equals("1"))count++;
      }
      System.out.println(count);
    }
} public class Main {
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
      String po[]=sc.nextLine().split("",0);
      int count=0;
      for(int i=0;i<3;i++){
      if(po[i].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 po[]=sc.nextLine().split("",0);
      int count=0;
      for(int i=0;i<3;i++){
      if(po[i].equals("1"))count++;
      }
      System.out.println(count);
    }
}
