import java.util.*;
import java.lang.*;
import java.io.*;
class Main {
public static void main(String[] args) {
Scanner s=new Scanner(System.in);
String str=s.next();
int answer=0;
for(int i=0;i<str.length();i++){
answer+=str.charAt(i)-'0';
}
System.out.println(answer);
}
}
k=list(input())
sum=0
for i in k:
sum+=int(i)
print(sum)