import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int count =0;
		char c[] = sc.next().toCharArray();
		for (int i=0;i<3;i++) {
			if (c[i]=='1') {
				count ++;
			}
		}
		System.out.println(count);
	}
} import java.util.Scanner; Scanner java.util public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int count =0;
		char c[] = sc.next().toCharArray();
		for (int i=0;i<3;i++) {
			if (c[i]=='1') {
				count ++;
			}
		}
		System.out.println(count);
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int count =0;
		char c[] = sc.next().toCharArray();
		for (int i=0;i<3;i++) {
			if (c[i]=='1') {
				count ++;
			}
		}
		System.out.println(count);
	} main {
		Scanner sc = new Scanner(System.in);
		int count =0;
		char c[] = sc.next().toCharArray();
		for (int i=0;i<3;i++) {
			if (c[i]=='1') {
				count ++;
			}
		}
		System.out.println(count);
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int count =0; count 0 char c[] = sc.next().toCharArray(); c sc.next().toCharArray() sc.next().toCharArray sc.next() sc.next sc for (int i=0;i<3;i++) {
			if (c[i]=='1') {
				count ++;
			}
		} int i=0; int i=0; i 0 i<3 i 3 i++ i++ i {
			if (c[i]=='1') {
				count ++;
			}
		} {
			if (c[i]=='1') {
				count ++;
			}
		} if (c[i]=='1') {
				count ++;
			} c[i]=='1' c[i] c i '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 sc = new Scanner(System.in);
		int count =0;
		char c[] = sc.next().toCharArray();
		for (int i=0;i<3;i++) {
			if (c[i]=='1') {
				count ++;
			}
		}
		System.out.println(count);
	}
} public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int count =0;
		char c[] = sc.next().toCharArray();
		for (int i=0;i<3;i++) {
			if (c[i]=='1') {
				count ++;
			}
		}
		System.out.println(count);
	}
} Main
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int count =0;
		char c[] = sc.next().toCharArray();
		for (int i=0;i<3;i++) {
			if (c[i]=='1') {
				count ++;
			}
		}
		System.out.println(count);
	}
}