import java.util.Scanner;
public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int cnt = 0;
		if(n/100 == 1) cnt++;
		if(n/10%10 == 1) cnt++;
		if(n%10 == 1) cnt++;
		System.out.println(cnt);
	}
} import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int cnt = 0;
		if(n/100 == 1) cnt++;
		if(n/10%10 == 1) cnt++;
		if(n%10 == 1) cnt++;
		System.out.println(cnt);
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int cnt = 0;
		if(n/100 == 1) cnt++;
		if(n/10%10 == 1) cnt++;
		if(n%10 == 1) cnt++;
		System.out.println(cnt);
	} main {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int cnt = 0;
		if(n/100 == 1) cnt++;
		if(n/10%10 == 1) cnt++;
		if(n%10 == 1) cnt++;
		System.out.println(cnt);
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc int cnt = 0; cnt 0 if(n/100 == 1) cnt++; n/100 == 1 n/100 n 100 1 cnt++ cnt if(n/10%10 == 1) cnt++; n/10%10 == 1 n/10%10 n/10 n 10 10 1 cnt++ cnt if(n%10 == 1) cnt++; n%10 == 1 n%10 n 10 1 cnt++ cnt System.out.println(cnt) System.out.println System.out System System.out cnt String[] args args public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int cnt = 0;
		if(n/100 == 1) cnt++;
		if(n/10%10 == 1) cnt++;
		if(n%10 == 1) cnt++;
		System.out.println(cnt);
	}
} public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int cnt = 0;
		if(n/100 == 1) cnt++;
		if(n/10%10 == 1) cnt++;
		if(n%10 == 1) cnt++;
		System.out.println(cnt);
	}
} Main
import java.util.Scanner;
public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int cnt = 0;
		if(n/100 == 1) cnt++;
		if(n/10%10 == 1) cnt++;
		if(n%10 == 1) cnt++;
		System.out.println(cnt);
	}
}