import java.util.Scanner;

public class Main {
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		String[] s = new String[n];
		String[] t = new String[n];
		for (int i = 0; i < n; i++) {
			s[i] = sc.next();
			t[i] = sc.next();
		}
		sc.close();

		for (int i = 0; i < n; i++) {
			boolean flg1 = true;
			boolean flg2 = true;
			for (int j = 0; j < n; j++) {
				if (i != j) {
					if (s[i].equals(s[j]) || s[i].equals(t[j])) {
						flg1 = false;
					}
					if (t[i].equals(s[j]) || t[i].equals(t[j])) {
						flg2 = false;
					}
				}
			}
			if (!flg1 && !flg2) {
				System.out.println("No");
				return;
			}
		}
		System.out.println("Yes");
	}
}