#include<stdio.h>
int strcmp(char s[], char t[])
{
	int i;
	for (i = 0;; i++)
	{
		if (s[i] == '\0' && t[i] == '\0')
			return 0;
		if (t[i] == '\0')
			return 1;
		if (s[i] == '\0')
			return -1;
		if (s[i] > t[i])
			return 1;
		if (s[i] < t[i])
			return -1;
	}
}
char s[102][2][32];
int main()
{
	int n;
	scanf("%d", &n);
	int i, j, k;
	for (i = 0; i < n; i++)
		scanf("%s%s", s[i][0], s[i][1]);
	for (i = 0; i < n; i++)
	{
		k = 0;
		for (j = 0; j < n; j++)
		{
			if (i == j)
				continue;
			if (strcmp(s[i][0], s[j][0]) == 0)
				k++;
			if (strcmp(s[i][0], s[j][1]) == 0)
				k++;
		}
		if (k == 0)
			continue;
		k = 0;
		for (j = 0; j < n; j++)
		{
			if (i == j)
				continue;
			if (strcmp(s[i][1], s[j][0]) == 0)
				k++;
			if (strcmp(s[i][1], s[j][1]) == 0)
				k++;
		}
		if (k == 0)
			continue;
		printf("No\n");
		return 0;
	}
	printf("Yes\n");
	return 0;
}