import java.util.Scanner;

public class Main {

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

        String si = sc.nextLine();
        int sum = 0;
        for (int i = 0; i < si.length(); i++) {
            char s = si.charAt(i);
            if (s == '1') {
                sum++;
            }
        }

        System.out.println(sum);
    }
} import java.util.Scanner; Scanner java.util public class Main {

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

        String si = sc.nextLine();
        int sum = 0;
        for (int i = 0; i < si.length(); i++) {
            char s = si.charAt(i);
            if (s == '1') {
                sum++;
            }
        }

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

        String si = sc.nextLine();
        int sum = 0;
        for (int i = 0; i < si.length(); i++) {
            char s = si.charAt(i);
            if (s == '1') {
                sum++;
            }
        }

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

        String si = sc.nextLine();
        int sum = 0;
        for (int i = 0; i < si.length(); i++) {
            char s = si.charAt(i);
            if (s == '1') {
                sum++;
            }
        }

        System.out.println(sum);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String si = sc.nextLine(); si sc.nextLine() sc.nextLine sc int sum = 0; sum 0 for (int i = 0; i < si.length(); i++) {
            char s = si.charAt(i);
            if (s == '1') {
                sum++;
            }
        } int i = 0; int i = 0; i 0 i < si.length() i si.length() si.length si i++ i++ i {
            char s = si.charAt(i);
            if (s == '1') {
                sum++;
            }
        } {
            char s = si.charAt(i);
            if (s == '1') {
                sum++;
            }
        } char s = si.charAt(i); s si.charAt(i) si.charAt si i if (s == '1') {
                sum++;
            } s == '1' s '1' {
                sum++;
            } sum++ sum System.out.println(sum) System.out.println System.out System System.out sum String[] args args public class Main {

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

        String si = sc.nextLine();
        int sum = 0;
        for (int i = 0; i < si.length(); i++) {
            char s = si.charAt(i);
            if (s == '1') {
                sum++;
            }
        }

        System.out.println(sum);
    }
} public class Main {

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

        String si = sc.nextLine();
        int sum = 0;
        for (int i = 0; i < si.length(); i++) {
            char s = si.charAt(i);
            if (s == '1') {
                sum++;
            }
        }

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

public class Main {

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

        String si = sc.nextLine();
        int sum = 0;
        for (int i = 0; i < si.length(); i++) {
            char s = si.charAt(i);
            if (s == '1') {
                sum++;
            }
        }

        System.out.println(sum);
    }
}
