import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String s = scanner.next();
        int count = 0;
        if (s.charAt(0)=='1'){
            count++;
        }
        if (s.charAt(1)=='1'){
            count++;
        }
        if (s.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 scanner = new Scanner(System.in);
        String s = scanner.next();
        int count = 0;
        if (s.charAt(0)=='1'){
            count++;
        }
        if (s.charAt(1)=='1'){
            count++;
        }
        if (s.charAt(2)=='1'){
            count++;
        }
        System.out.println(count);
    }
} Main public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String s = scanner.next();
        int count = 0;
        if (s.charAt(0)=='1'){
            count++;
        }
        if (s.charAt(1)=='1'){
            count++;
        }
        if (s.charAt(2)=='1'){
            count++;
        }
        System.out.println(count);
    } main {
        Scanner scanner = new Scanner(System.in);
        String s = scanner.next();
        int count = 0;
        if (s.charAt(0)=='1'){
            count++;
        }
        if (s.charAt(1)=='1'){
            count++;
        }
        if (s.charAt(2)=='1'){
            count++;
        }
        System.out.println(count);
    } Scanner scanner = new Scanner(System.in); scanner new Scanner(System.in) String s = scanner.next(); s scanner.next() scanner.next scanner int count = 0; count 0 if (s.charAt(0)=='1'){
            count++;
        } s.charAt(0)=='1' s.charAt(0) s.charAt s 0 '1' {
            count++;
        } count++ count if (s.charAt(1)=='1'){
            count++;
        } s.charAt(1)=='1' s.charAt(1) s.charAt s 1 '1' {
            count++;
        } count++ count if (s.charAt(2)=='1'){
            count++;
        } s.charAt(2)=='1' s.charAt(2) s.charAt s 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 s = scanner.next();
        int count = 0;
        if (s.charAt(0)=='1'){
            count++;
        }
        if (s.charAt(1)=='1'){
            count++;
        }
        if (s.charAt(2)=='1'){
            count++;
        }
        System.out.println(count);
    }
} public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String s = scanner.next();
        int count = 0;
        if (s.charAt(0)=='1'){
            count++;
        }
        if (s.charAt(1)=='1'){
            count++;
        }
        if (s.charAt(2)=='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 s = scanner.next();
        int count = 0;
        if (s.charAt(0)=='1'){
            count++;
        }
        if (s.charAt(1)=='1'){
            count++;
        }
        if (s.charAt(2)=='1'){
            count++;
        }
        System.out.println(count);
    }
}