#include <bits/stdc++.h>
using namespace std;
int n;
int f[55][55][55][55];
string s[100];
bool dfs(int n, int a, int b, int c) {
  if (n == 1) return 1;
  if (f[n][a][b][c]) return 0;
  if (s[c][0] == s[b][0] || s[c][1] == s[b][1])
    if (dfs(n - 1, n - 3, a, c)) return 1;
  if (n > 3 && (s[c][0] == s[n - 3][0] || s[c][1] == s[n - 3][1]))
    if (dfs(n - 1, c, a, b)) return 1;
  f[n][a][b][c] = 1;
  return 0;
}
int main() {
  scanf("%d", &n);
  for (int i = 1; i <= n; i++) cin >> s[i];
  bool ans = dfs(n, n - 2, n - 1, n);
  if (ans == 0)
    cout << "NO" << endl;
  else
    cout << "YES" << endl;
  return 0;
}
