#include <bits/stdc++.h>
using namespace std;
const long long N = 1e6 + 5, inf = 1e18, mod = 1e9 + 7;
const long double pi = 3.141592653589793238;
bool check_prime(long long n) {
  long long flag = 0, i;
  for (i = 2; i * i <= n; i++) {
    if (n % i == 0) {
      flag = 1;
      break;
    }
  }
  if (n == 1) {
    return false;
  } else if (flag == 0 || n == 2 || n == 3) {
    return true;
  } else {
    return false;
  }
}
long long fastexpo(long long a, long long b, long long MOD) {
  long long result = 1;
  while (b > 0) {
    if (b % 2 == 1) {
      result = (result * a) % MOD;
    }
    a = (a * a) % MOD;
    b = b / 2;
  }
  return result;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  long long n, i, p, c;
  cin >> n;
  set<long long> s;
  s.insert(n);
  c = 0;
  if (n == 1) {
    c++;
  }
  while (1) {
    n++;
    for (i = 1;; i++) {
      p = pow(10, i);
      if (n % p != 0) {
        p = p / 10;
        break;
      }
    }
    n /= p;
    s.insert(n);
    if (n == 1) {
      c++;
      if (c == 2) {
        break;
      }
    }
  }
  cout << ((long long)((s).size())) << "\n";
  return 0;
}
