#include <bits/stdc++.h>
std::string colors("RGBYW");
struct Card {
  int color;
  int number;
  bool operator<(const Card& rhs) const {
    if (color == rhs.color)
      return (number < rhs.number);
    else
      return color < rhs.color;
  }
};
int mapColor(char color) {
  size_t pos = colors.find_first_of(color);
  if (pos != std::string::npos) {
    return pos;
  }
  return -1;
}
bool isNumberHinted(int number, long long hint) {
  long long mask = (1 << number) << 5;
  return hint & mask;
}
bool isColorHinted(int color, long long hint) {
  long long mask = (1 << color);
  return hint & mask;
}
int bitCount(long long n) {
  int count = 0;
  while (n > 0) {
    count++;
    n = n & (n - 1);
  }
  return count;
}
void codeforces442a() {
  int n = 0;
  int minAns = 10;
  std::cin >> n;
  std::set<Card> cards;
  for (int i = 0; i < n; ++i) {
    Card card;
    char color;
    char number;
    std::cin >> color;
    std::cin >> number;
    card.color = mapColor(color);
    card.number = number - '1';
    cards.insert(card);
  }
  if (cards.size() == 1) {
    std::cout << "0";
    return;
  }
  for (long long hint = 0; hint < (1 << 10); ++hint) {
    if (bitCount(hint) >= minAns) continue;
    bool isValid = true;
    for (std::set<Card>::iterator i = cards.begin();
         i != cards.end() && isValid; ++i)
      for (std::set<Card>::iterator j = cards.begin();
           j != cards.end() && isValid; ++j) {
        if (i != j) {
          bool areHintedAsDifferent = false;
          Card firstCard = *i;
          Card secondCard = *j;
          if (firstCard.color == secondCard.color) {
            areHintedAsDifferent = isNumberHinted(firstCard.number, hint) ||
                                   isNumberHinted(secondCard.number, hint);
          } else if (firstCard.number == secondCard.number) {
            areHintedAsDifferent = isColorHinted(firstCard.color, hint) ||
                                   isColorHinted(secondCard.color, hint);
          } else {
            areHintedAsDifferent = isNumberHinted(firstCard.number, hint) ||
                                   isNumberHinted(secondCard.number, hint) ||
                                   isColorHinted(firstCard.color, hint) ||
                                   isColorHinted(secondCard.color, hint);
          }
          if (!areHintedAsDifferent) {
            isValid = false;
          }
        }
      }
    if (isValid) {
      int numHints = bitCount(hint);
      if (minAns > numHints) {
        minAns = numHints;
      }
    }
  }
  std::cout << minAns;
}
int main() {
  codeforces442a();
  return 0;
}
