#include <bits/stdc++.h>
using namespace std;
int n;
vector<string> cards;
map<vector<string>, bool> used;
void rec(vector<string>& x) {
  if (x.size() == 1) {
    puts("YES");
    exit(0);
  }
  if (used[x] == true) return;
  used[x] = true;
  int p = x.size() - 1;
  if (x[p][0] == x[p - 1][0] || x[p][1] == x[p - 1][1]) {
    string s = x[p - 1];
    string c = x[p];
    x[p - 1] = x[p];
    x.pop_back();
    rec(x);
    x[p - 1] = s;
    x.push_back(c);
  }
  if (p > 2 && (x[p][0] == x[p - 3][0] || x[p][1] == x[p - 3][1])) {
    string s = x[p - 3];
    string c = x[p];
    x[p - 3] = x[p];
    x.pop_back();
    rec(x);
    x[p - 3] = s;
    x.push_back(c);
  }
}
int main() {
  cin >> n;
  for (int i = 0; i < n; i++) {
    string s;
    cin >> s;
    cards.push_back(s);
  }
  rec(cards);
  puts("NO");
  return 0;
}
