#include <bits/stdc++.h>
#define REP(A,B) for(int (A)=0;(A)<(B);(A)++)
using namespace std;
#define ll long long
#define pb push_back
char str[5];
typedef vector<int> VI;
typedef vector<VI> VVI;
bool FindMatch(int i, const VVI& w, VI&mr, VI&mc, VI& seen) {
	REP(j, w[i].size()) {
		if(w[i][j]&&!seen[j]) {
			seen[j]=true;
			if(mc[j]<0 || FindMatch(mc[j], w, mr, mc, seen)) {
				mr[i]=j;
				mc[j]=i;
				return true;
			}
		}
	}
	return false;
}
int BipartiteMatching(const VVI &w, VI& mr, VI&mc) {
	mr = VI(w.size(), -1);
	mc = VI(w[0].size(), -1);
	int ct = 0;
	REP(i, w.size()) {
		VI seen(w[0].size());
		if(FindMatch(i, w, mr, mc, seen))
			ct++;
	}
	return ct;
}

int main() {
	int n;
	while(scanf("%d", &n)==1) {
		vector<string> cards;
		REP(i, n) {
			scanf("%s", str);
			cards.pb(string(str));
		//	printf("%s ", cards.back().c_str());
		}
		vector<vector<int>> Graph;
		REP(i, 2*n) {
			Graph.pb(vector<int>());
			REP(j, 2*n) Graph[i].pb(0);
		}
		REP(i, n) REP(j, n) {
			if(i != j) {
				bool yes = false;
				if(cards[i][0]==cards[j][0]) {
					Graph[2*i+1][2*j] = Graph[2*j][2*i+1] = 1;
					yes = true;
				} else if(cards[i][1]==cards[j][1]) {
					Graph[2*i+1][2*j] = Graph[2*j][2*i+1] = 1;
					yes = true;
				}
//				if(yes) printf("edge from %d to %d (%d %d)\n", i, j, 2*i+1, j);
			}
		}
		VI RM, CM;
		int M = BipartiteMatching(Graph, RM, CM);
//		printf("%d\n", M);
		printf("%s\n", M >= 2*(n-1) ? "YES" : "NO");
	}
	return 0;
}