// https://omegaup.com/arena/problem/Suma-de-los-digitos 
#include <stdio.h> 
 
int main( ) { 
   int n, suma = 0; 
   scanf("%d", &n); 
 
   while (n != 0) { 
      int c = n / 10; 
      int r = n % 10; 
      suma += r; 
      n = c; 
   } 
 
   printf("%d", suma); 
}