#include <bits/stdc++.h>
using namespace std;
bool IsPrime(int n) {
  if (n == 1) return false;
  for (int d = 2; d * d <= n; d++) {
    if (n % d == 0) return false;
  }
  return true;
}
int main() {
  int n;
  cin >> n;
  int count = 0;
  while (n > 0) {
    int j = 0;
    int k = n;
    int amx = INT_MIN;
    while (k > 0) {
      j = k % 10;
      k = k / 10;
      amx = max(amx, j);
    }
    n -= amx;
    count++;
  }
  cout << count << endl;
  return 0;
}
