import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
String str = scan.next();
int sum = 0;
for(int i = 0; i < str.length(); i++) {
String xstr = str.substring(i, i + 1);
int x = Integer.parseInt(xstr);
sum += x;
}
System.out.println(sum);
}
}