#include <iostream>
#include <cstdio>
#include <set>
#include <map>
#include<string>
#include<vector>
// #include <multiset>
#include<queue>
#include<cstring>

using namespace std;

int main()
{
	int M;
	string s;
	vector<string> card;
	queue<int> q;
	int exist[1000];
	int proc[1000];

	while (scanf("%d", &M) == 1) {
		card.clear();

		memset(exist, 0, sizeof exist);
		memset(proc, 0, sizeof proc);

		for(int i=0; i<M; ++i) {
			cin >> s;
			card.push_back(s);
		}

		q.push(0);
		exist[0] = 1;

		while (!q.empty()) {
			int p = q.front();
			q.pop();

			if (proc[p]) {
				continue;
			}

			for (int j=0; j<M; ++j) {
				if (j == p) {
					continue;
				}

				if (card[p][0] == card[j][0] || card[p][1] == card[j][1]) {
					exist[j] = 1;
					q.push(j);
				}
			}

			proc[p] = 1;
		}

		int res = 1;

		for (int i=0; i<M; ++i) {
			if (!exist[i]) {
				res = 0;
			}
		}

		printf("%s\n", res ? "YES" : "NO");
	}

	return 0;
}