import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String[] array = sc.nextLine().split("");
        int sum = 0;
        for (String s : array) {
            if (Integer.parseInt(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[] array = sc.nextLine().split("");
        int sum = 0;
        for (String s : array) {
            if (Integer.parseInt(s) == 1) {
                sum++;
            }
        }
        System.out.println(sum);
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String[] array = sc.nextLine().split("");
        int sum = 0;
        for (String s : array) {
            if (Integer.parseInt(s) == 1) {
                sum++;
            }
        }
        System.out.println(sum);
    } main {
        Scanner sc = new Scanner(System.in);
        String[] array = sc.nextLine().split("");
        int sum = 0;
        for (String s : array) {
            if (Integer.parseInt(s) == 1) {
                sum++;
            }
        }
        System.out.println(sum);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String[] array = sc.nextLine().split(""); array sc.nextLine().split("") sc.nextLine().split sc.nextLine() sc.nextLine sc "" int sum = 0; sum 0 for (String s : array) {
            if (Integer.parseInt(s) == 1) {
                sum++;
            }
        } String s array {
            if (Integer.parseInt(s) == 1) {
                sum++;
            }
        } {
            if (Integer.parseInt(s) == 1) {
                sum++;
            }
        } if (Integer.parseInt(s) == 1) {
                sum++;
            } Integer.parseInt(s) == 1 Integer.parseInt(s) Integer.parseInt Integer 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[] array = sc.nextLine().split("");
        int sum = 0;
        for (String s : array) {
            if (Integer.parseInt(s) == 1) {
                sum++;
            }
        }
        System.out.println(sum);
    }
} public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String[] array = sc.nextLine().split("");
        int sum = 0;
        for (String s : array) {
            if (Integer.parseInt(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[] array = sc.nextLine().split("");
        int sum = 0;
        for (String s : array) {
            if (Integer.parseInt(s) == 1) {
                sum++;
            }
        }
        System.out.println(sum);
    }
}
