#include <bits/stdc++.h>
using std::cerr;
using std::cin;
using std::cout;
using std::endl;
using std::list;
using std::map;
using std::max;
using std::min;
using std::pair;
using std::set;
using std::sort;
using std::string;
using std::swap;
using std::vector;
const int MAXN = 100005;
const long long INF = 100000000009;
const long long MOD = (long long)1e9 + 7;
bool used[MAXN];
bool cnt[MAXN][50];
int main() {
  std::ios_base::sync_with_stdio(false);
  std::cin.tie(nullptr);
  int n;
  cin >> n;
  string sec;
  cin >> sec;
  for (int i = 0; i < n; ++i) {
    if (sec[i] != '*') {
      used[(int)sec[i]] = true;
    }
  }
  int m;
  cin >> m;
  vector<string> needed;
  for (int i = 0; i < m; ++i) {
    string s;
    cin >> s;
    bool flag = true;
    for (int j = 0; j < n; ++j) {
      if (sec[j] == '*') {
        if (used[(int)s[j]]) {
          flag = false;
          break;
        }
      } else if (sec[j] != s[j]) {
        flag = false;
        break;
      }
    }
    if (flag) {
      needed.push_back(s);
    }
  }
  for (int j = 0; j < needed.size(); ++j) {
    for (int i = 0; i < n; ++i) {
      if (sec[i] == '*') {
        cnt[j][(int)needed[j][i] - 'a'] = true;
      }
    }
  }
  int ans = 0;
  for (int i = 0; i <= (int)'z' - (int)'a'; ++i) {
    bool flag = true;
    for (int j = 0; j < needed.size(); ++j) {
      if (!cnt[j][i]) {
        flag = false;
      }
    }
    if (flag) {
      ++ans;
    }
  }
  cout << ans;
  return 0;
}
