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;
        if(s2[0].equals("1")){
            count++;
        }
        if(s2[1].equals("1")){
            count++;
        }
        if(s2[2].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;
        if(s2[0].equals("1")){
            count++;
        }
        if(s2[1].equals("1")){
            count++;
        }
        if(s2[2].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;
        if(s2[0].equals("1")){
            count++;
        }
        if(s2[1].equals("1")){
            count++;
        }
        if(s2[2].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;
        if(s2[0].equals("1")){
            count++;
        }
        if(s2[1].equals("1")){
            count++;
        }
        if(s2[2].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 if(s2[0].equals("1")){
            count++;
        } s2[0].equals("1") s2[0].equals s2[0] s2 0 "1" {
            count++;
        } count++ count if(s2[1].equals("1")){
            count++;
        } s2[1].equals("1") s2[1].equals s2[1] s2 1 "1" {
            count++;
        } count++ count if(s2[2].equals("1")){
            count++;
        } s2[2].equals("1") s2[2].equals s2[2] s2 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 scanner = new Scanner(System.in);
        String s1 = scanner.next();
        String s2[] = s1.split("");
        int count = 0;
        if(s2[0].equals("1")){
            count++;
        }
        if(s2[1].equals("1")){
            count++;
        }
        if(s2[2].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;
        if(s2[0].equals("1")){
            count++;
        }
        if(s2[1].equals("1")){
            count++;
        }
        if(s2[2].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;
        if(s2[0].equals("1")){
            count++;
        }
        if(s2[1].equals("1")){
            count++;
        }
        if(s2[2].equals("1")){
            count++;
        }

        System.out.println(count);
    }
}