import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String s1 = scanner.next();
        String s2[] = s1.split("");
        int count = 0;
      
        for(int i =0; i < s2.length; i++){
            if(s2[i].equals("1")){
                count++;
            }
        }

        System.out.println(count);
    }
} import java.util.Scanner; Scanner java.util public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String s1 = scanner.next();
        String s2[] = s1.split("");
        int count = 0;
      
        for(int i =0; i < s2.length; i++){
            if(s2[i].equals("1")){
                count++;
            }
        }

        System.out.println(count);
    }
} Main public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String s1 = scanner.next();
        String s2[] = s1.split("");
        int count = 0;
      
        for(int i =0; i < s2.length; i++){
            if(s2[i].equals("1")){
                count++;
            }
        }

        System.out.println(count);
    } main {
        Scanner scanner = new Scanner(System.in);
        String s1 = scanner.next();
        String s2[] = s1.split("");
        int count = 0;
      
        for(int i =0; i < s2.length; i++){
            if(s2[i].equals("1")){
                count++;
            }
        }

        System.out.println(count);
    } Scanner scanner = new Scanner(System.in); scanner new Scanner(System.in) String s1 = scanner.next(); s1 scanner.next() scanner.next scanner String s2[] = s1.split(""); s2 s1.split("") s1.split s1 "" int count = 0; count 0 for(int i =0; i < s2.length; i++){
            if(s2[i].equals("1")){
                count++;
            }
        } int i =0; int i =0; i 0 i < s2.length i s2.length s2 s2.length i++ i++ i {
            if(s2[i].equals("1")){
                count++;
            }
        } {
            if(s2[i].equals("1")){
                count++;
            }
        } if(s2[i].equals("1")){
                count++;
            } s2[i].equals("1") s2[i].equals s2[i] s2 i "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 scanner = new Scanner(System.in);
        String s1 = scanner.next();
        String s2[] = s1.split("");
        int count = 0;
      
        for(int i =0; i < s2.length; i++){
            if(s2[i].equals("1")){
                count++;
            }
        }

        System.out.println(count);
    }
} public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String s1 = scanner.next();
        String s2[] = s1.split("");
        int count = 0;
      
        for(int i =0; i < s2.length; i++){
            if(s2[i].equals("1")){
                count++;
            }
        }

        System.out.println(count);
    }
} Main
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String s1 = scanner.next();
        String s2[] = s1.split("");
        int count = 0;
      
        for(int i =0; i < s2.length; i++){
            if(s2[i].equals("1")){
                count++;
            }
        }

        System.out.println(count);
    }
}
