#include<stdio.h>
struct Number {
    int value;
};

int main(){
    struct Number n;
    int sum = 0;
    scanf("%d", &n.value);
    printf("Invalid input\n");
    return 0;
  }
  int temp = n.value;
  while (temp > 0){
      sum += temp %10;
      temp /= 10;
  }
  printf("%d\n", sum);
  return 0;
  }