#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int t = 1, n, k = 0, flag = -1, b = 0;
  while (t--) {
    scanf("%lld", &n);
    k = 0;
    while (n != flag) {
      if (n / 10 == 0 && b == 0) {
        flag = n;
        b = 1;
      }
      k++;
      n++;
      while (n % 10 == 0) {
        n = n / 10;
      }
    }
    printf("%lld\n", k);
  }
  return 0;
}
