import java.util.Scanner;

public class Main{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int x = sc.nextInt();
		
		System.out.println(x/100%10+x/10%10+x%10);
		
	}

}
/**************************************************************
	Problem: 1716
	User: admin
	Language: Java
	Result: Accepted
	Time:2325 ms
	Memory:40284 kb
****************************************************************/