#include <stdio.h>
int cards[53][4], n;

int dfs(int x)
{
	int i, ma = 0, t;
	for (i = 0; i < n; i++)
		if (cards[i][3] == 0)
			if ((cards[x][0] == cards[i][0]) || (cards[x][1] == cards[i][1])) {
				cards[i][3] = 1;
				t = dfs(i);
				if (t > ma) ma = t; }
	return t + 1;	
}

int main()
{
	int i, j, obchod[53], count, obchodchik, answer, k;
	char c1, c2;
	while (scanf("%d", &n) != EOF)
	{
		if (n == 1) {
			printf("YES\n");
			continue; }
		scanf("%c", &c1);
		for (i = 0; i < n; i++)
		{
			scanf("%c%c", &c1, &c2);
			scanf("%c");
			//printf("%c%c ", c1, c2);
			cards[i][0] = (int)c1;
			cards[i][1] = (int)c2;
			cards[i][2] = 0;
			cards[i][3] = 0;
		}
		
		count = 0;
		obchod[0] = 0;
		obchodchik = 0;
		cards[0][3] = 1;
		//for (i = 0; i < n; i++) printf("((cards[i][0] == cards[j][0]) || (cards[i][1] == cards[j][1]))%d. %c%c - %d %d\n", i, (char)cards[i][0], (char)cards[i][1], cards[i][2], cards[i][3]);
		while (obchodchik <= count)
		{
			for (i = 0; i < n; i++) 
				if (cards[i][3] == 0) 
					if ((cards[obchod[obchodchik]][0] == cards[i][0]) || (cards[obchod[obchodchik]][1] == cards[i][1])) {
						//printf("nomer %d stepen %d\n", cards[i][2]);
						cards[i][3] = 1;
						obchod[++count] = i; }
			obchodchik++;
		}
		//for (i = 0; i < n; i++) printf("%d. kod %d %d - stepen %d obchod %d\n", i, cards[i][0], cards[i][1], cards[i][2], cards[i][3]);
		if (count < (n - 1)) {
			printf("NO\n");
			continue;
		}
		/*for (i = 0; i < n; i++)
			for (j = 0; j < n; j++)
				if ((i != j) && ((cards[i][0] == cards[j][0]) || (cards[i][1] == cards[j][1])))
					cards[i][2]++;
		for (i = 0; i < n; i++) printf("%d. kod %d %d - stepen %d obchod %d\n", i, cards[i][0], cards[i][1], cards[i][2], cards[i][3]);
		zeros = 0;
		odd = 0;
		for (i = 0; i < n; i++) {
			if (cards[i][2] == 0) zeros++;
			if ((cards[i][2] % 2) == 1) odd++; }*/
		k = 0;
		for (i = 0; i < n; i++) {
			k = dfs(i);
			if (k > answer) answer = k; }
		if (answer = n - 1) printf("YES\n");
		else printf("NO\n");	
					
	}
	return 0;
}