#include <iostream>
#include <vector>

using namespace std;

typedef struct card
{
	char rank, suit;
	bool used = false;
} Card;

vector<Card *> cards;

bool done = false;

bool recursion(int depth, Card * parent)
{
	if (done) return true;
	if (depth == cards.size()) {
		done = true;
		return true;
	}
	
	bool ret = false;
	
	for (const auto & card : cards)
	{
		if (done) return true;
		if (card->used == false)
		{
			if (parent != NULL) if (card->rank != parent->rank && card->suit != parent->suit) continue;
			card->used = true;
			ret = ret || recursion(depth + 1, card);
			card->used = false;
		}
	}
	
	return ret;
}

int main(int argc, char ** argv)
{
	int n;
	while (cin >> n)
	{
		bool fail = false;
	done = false;
		for (int i = 0; i < n; ++i)
		{
			char c;
			Card * temp = new Card();
			scanf("%c%c%c", &c, &temp->rank, &temp->suit);
			cards.push_back(temp);
		}

		int cnt = 0;
		for (int i = 0; i < cards.size(); ++i)
		{
			bool flag = false;
			for (int j = 0; j < cards.size(); ++j)
			{
				if (i!=j && (cards[i]->rank == cards[j]->rank || cards[i]->suit == cards[j]->suit)) 
				{
					cnt++;
					flag = true;
				}
			}
			if (flag == false)
			{
				fail = true;
				break;
			}
		}

		
		if (cnt < n - 1 || fail == true) 
		{
			cout << "NO" << endl;
			cards.clear();
			continue;
		}
		
		bool a = recursion(0, NULL);
		if (a) cout << "YES" << endl;
		else cout << "NO" << endl;
		cards.clear();
	}


	return 0;
}