#include <bits/stdc++.h>
using namespace std;
char op[] = {'R', 'G', 'B', 'Y', 'W', '1', '2', '3', '4', '5'};
string s[555];
int main() {
  int n, i, j, k;
  ios_base::sync_with_stdio(0), cin.tie(0);
  cin >> n;
  for (i = 1; i <= n; i++) {
    cin >> s[i];
  }
  map<char, bool> mp;
  int mn = 100000;
  for (int msk = 0; msk < (1024); msk++) {
    mp.clear();
    for (i = 0; i < 10; i++) {
      if (msk & (1 << i)) {
        mp[op[i]] = 1;
      }
    }
    bool f = 1;
    for (i = 1; i <= n; i++) {
      for (j = i + 1; j <= n; j++) {
        if (s[i] == s[j]) continue;
        if (s[i][0] == s[j][0]) {
          if (!mp[s[i][1]] && !mp[s[j][1]]) {
            f = 0;
            break;
          }
        } else if (s[i][1] == s[j][1]) {
          if (!mp[s[i][0]] && !mp[s[j][0]]) {
            f = 0;
            break;
          }
        } else {
          if (!mp[s[i][1]] && !mp[s[j][1]] && !mp[s[i][0]] && !mp[s[j][0]]) {
            f = 0;
            break;
          }
        }
      }
      if (!f) break;
    }
    if (f == 1) mn = min(mn, __builtin_popcount(msk));
  }
  cout << mn << endl;
}
