import java.util.*;

public class Main {
    static Scanner scanner = new Scanner(System.in);

    public static void main(String[]$) {
        System.out.println(Integer.bitCount(Integer.parseInt(scanner.next(), 2)));
    }
} import java.util.*; util.* java public class Main {
    static Scanner scanner = new Scanner(System.in);

    public static void main(String[]$) {
        System.out.println(Integer.bitCount(Integer.parseInt(scanner.next(), 2)));
    }
} Main static Scanner scanner = new Scanner(System.in); scanner new Scanner(System.in) public static void main(String[]$) {
        System.out.println(Integer.bitCount(Integer.parseInt(scanner.next(), 2)));
    } main {
        System.out.println(Integer.bitCount(Integer.parseInt(scanner.next(), 2)));
    } System.out.println(Integer.bitCount(Integer.parseInt(scanner.next(), 2))) System.out.println System.out System System.out Integer.bitCount(Integer.parseInt(scanner.next(), 2)) Integer.bitCount Integer Integer.parseInt(scanner.next(), 2) Integer.parseInt Integer scanner.next() scanner.next scanner 2 String[]$ $ public class Main {
    static Scanner scanner = new Scanner(System.in);

    public static void main(String[]$) {
        System.out.println(Integer.bitCount(Integer.parseInt(scanner.next(), 2)));
    }
} public class Main {
    static Scanner scanner = new Scanner(System.in);

    public static void main(String[]$) {
        System.out.println(Integer.bitCount(Integer.parseInt(scanner.next(), 2)));
    }
} Main
import java.util.*;

public class Main {
    static Scanner scanner = new Scanner(System.in);

    public static void main(String[]$) {
        System.out.println(Integer.bitCount(Integer.parseInt(scanner.next(), 2)));
    }
}