#include <bits/stdc++.h>
using namespace std;
int main() {
  long long k, sum = 0, i, j, n, cnt = 0;
  int a[20] = {0}, value;
  string s;
  cin >> k;
  cin >> s;
  for (i = 0; i < ((int)s.size()); ++i) {
    n = s[i] - '0';
    sum += n;
    a[n]++;
  }
  if (sum >= k) {
    cout << cnt << endl;
    return 0;
  }
  for (i = 0; i < 10; ++i) {
    value = 9 - i;
    for (j = 1; j <= a[i]; ++j) {
      sum += value;
      cnt++;
      if (sum >= k) {
        cout << cnt << endl;
        return 0;
      }
    }
  }
}
