import java.util.Scanner;

public class Main{
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        String input = sc.nextLine();
        byte count = 0;

        if(input.charAt(0) == '1'){
            count++;
        }
        if(input.charAt(1) == '1'){
            count++;
        }
        if(input.charAt(2) == '1'){
            count++;
        }

        System.out.println(count);

    }
} import java.util.Scanner; Scanner java.util public class Main{
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        String input = sc.nextLine();
        byte count = 0;

        if(input.charAt(0) == '1'){
            count++;
        }
        if(input.charAt(1) == '1'){
            count++;
        }
        if(input.charAt(2) == '1'){
            count++;
        }

        System.out.println(count);

    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        String input = sc.nextLine();
        byte count = 0;

        if(input.charAt(0) == '1'){
            count++;
        }
        if(input.charAt(1) == '1'){
            count++;
        }
        if(input.charAt(2) == '1'){
            count++;
        }

        System.out.println(count);

    } main {
        Scanner sc = new Scanner(System.in);

        String input = sc.nextLine();
        byte count = 0;

        if(input.charAt(0) == '1'){
            count++;
        }
        if(input.charAt(1) == '1'){
            count++;
        }
        if(input.charAt(2) == '1'){
            count++;
        }

        System.out.println(count);

    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String input = sc.nextLine(); input sc.nextLine() sc.nextLine sc byte count = 0; count 0 if(input.charAt(0) == '1'){
            count++;
        } input.charAt(0) == '1' input.charAt(0) input.charAt input 0 '1' {
            count++;
        } count++ count if(input.charAt(1) == '1'){
            count++;
        } input.charAt(1) == '1' input.charAt(1) input.charAt input 1 '1' {
            count++;
        } count++ count if(input.charAt(2) == '1'){
            count++;
        } input.charAt(2) == '1' input.charAt(2) input.charAt input 2 '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 input = sc.nextLine();
        byte count = 0;

        if(input.charAt(0) == '1'){
            count++;
        }
        if(input.charAt(1) == '1'){
            count++;
        }
        if(input.charAt(2) == '1'){
            count++;
        }

        System.out.println(count);

    }
} public class Main{
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        String input = sc.nextLine();
        byte count = 0;

        if(input.charAt(0) == '1'){
            count++;
        }
        if(input.charAt(1) == '1'){
            count++;
        }
        if(input.charAt(2) == '1'){
            count++;
        }

        System.out.println(count);

    }
} Main
import java.util.Scanner;

public class Main{
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        String input = sc.nextLine();
        byte count = 0;

        if(input.charAt(0) == '1'){
            count++;
        }
        if(input.charAt(1) == '1'){
            count++;
        }
        if(input.charAt(2) == '1'){
            count++;
        }

        System.out.println(count);

    }
}