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

int dfs(int x)
{
	int i, ma = 0, t;
	//printf("dfs %d:\n", x);
	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;
				//printf("Chotim obojti %d\n", i);
				t = dfs(i);
				if ((t + 1) > ma) ma = t + 1; }
	return ma;	
}

int main()
{
	int i, j, obchod[53], k, ma1, ma2, stepen;
	char c1, c2;
	while (scanf("%d", &n) != EOF)
	{
		for (i = 0; i < n; i++)
			for (j = 0; j < 4; j++)
				cards[i][j] = 0;
		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;
		}
		/*if (n == 1) {
			printf("YES\n");
			continue; }*/
		k = 0;
		cards[0][3] = 1;
		ma1 = 0;
		ma2 = 0;
		stepen = 0;
		//for (i = 0; i < n; i++) printf("%d. %c%c\n", i, (char)cards[i][0], (char)cards[i][1]);
		for (i = 1; i < n; i++) 
			if ((cards[0][0] == cards[i][0]) || (cards[0][1] == cards[i][1])) {
				stepen++;
				cards[i][3] = 1;
				k = dfs(i);
				//printf("oboshli %d - glubina %d\n", i, k);
				if (k >= ma1) {
					ma2 = ma1;
					ma1 = k; }
				else
					if (k > ma2) ma2 = k; }
		if ((stepen == 1) && (ma1 >= (n - 2))) printf("YES\n");
		else
			if ((stepen >= 2) && (ma1 + ma2 >= (n - 3))) printf("YES\n");
			else printf("NO\n");	
					
	}
	return 0;
}