#include <bits/stdc++.h>
using namespace std;
int MOD = 1e9 + 7;
long long int power(long long int a, long long int b) {
  long long int res = 1;
  a = a % MOD;
  while (b > 0) {
    if (b & 1) {
      res = (res * a) % MOD;
      b--;
    }
    a = (a * a) % MOD;
    b >>= 1;
  }
  return res;
}
long long int fermat_inv(long long int y) { return power(y, MOD - 2); }
long long int gcd(long long int a, long long int b) {
  return (b == 0) ? a : gcd(b, a % b);
}
long long int min(long long int a, long long int b) { return (a > b) ? b : a; }
long long int max(long long int a, long long int b) { return (a > b) ? a : b; }
bool prime[1000001];
vector<int> primes;
void SieveOfEratosthenes(int n) {
  memset(prime, true, sizeof(prime));
  for (int p = 2; p * p <= n; p++) {
    if (prime[p] == true) {
      for (int i = p * p; i <= n; i += p) prime[i] = false;
    }
  }
  for (int p = 2; p < 1000001; p++)
    if (prime[p]) primes.push_back(p);
}
long long int fact[100005];
long long int finv[100005];
void factorial(int n) {
  fact[0] = 1;
  finv[0] = 1;
  for (int i = 1; i <= n; i++)
    fact[i] = fact[i - 1] * i, fact[i] %= MOD, finv[i] = fermat_inv(fact[i]);
}
long long int ncr(long long int n, long long int r) {
  if (n < r)
    return 0;
  else {
    long long int x = finv[r] * finv[n - r] % MOD;
    return fact[n] * x % MOD;
  }
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int t = 1;
  while (t--) {
    int n;
    cin >> n;
    string r;
    int m;
    cin >> r >> m;
    string s[m];
    for (int i = 0; i < m; i++) cin >> s[i];
    int ans = 0;
    vector<char> v1, v2;
    for (char c = 'a'; c <= 'z'; c++) {
      bool b = true;
      for (int i = 0; i < n; i++) {
        if (r[i] == c) {
          b = false;
          break;
        }
      }
      if (b)
        v1.push_back(c);
      else
        v2.push_back(c);
    }
    vector<string> g;
    for (int i = 0; i < m; i++) {
      bool b = true;
      for (int j = 0; j < n; j++) {
        if (r[j] != '*') {
          if (s[i][j] != r[j]) {
            b = false;
            break;
          }
        } else {
          for (char c : v2) {
            if (s[i][j] == c) {
              b = false;
              break;
            }
          }
        }
      }
      if (b) g.push_back(s[i]);
    }
    m = g.size();
    for (char c : v1) {
      int cnt = 0;
      for (string i : g) {
        for (char j : i) {
          if (j == c) {
            cnt++;
            break;
          }
        }
      }
      if (cnt == m) ans++;
    }
    cout << ans;
  }
}
