import java.io.*;
import java.util.HashSet;
import java.util.Set;
import java.util.StringTokenizer;

public class Main {
    public static void main(String[] args) {
        int n = sc.nextInt();
        String[][] s = new String[n][2];
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < 2; j++) {
                s[i][j] = sc.next();
            }
        }
        boolean ok = true;
        o:
        for (int i = 0; i < n; i++) {
            for (int j = i + 1; j < n; j++) {
                if ((s[i][0].equals(s[j][0]) && s[i][1].equals(s[j][1])) || (s[i][0].equals(s[j][1]) && s[i][1].equals(s[j][0]))) {
                    ok = false;
                    break o;
                }
            }
        }

        out.println(ok ? "Yes" : "No");

        out.close();
    }

    static Kattio sc = new Kattio();
    static PrintWriter out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(System.out)));

    static class Kattio {
        static BufferedReader r;
        static StringTokenizer st;

        public Kattio() {
            r = new BufferedReader(new InputStreamReader(System.in));
        }

        public String next() {
            try {
                while (st == null || !st.hasMoreTokens()) {
                    st = new StringTokenizer(r.readLine());
                }
                return st.nextToken();
            } catch (Exception e) {
                return null;
            }
        }

        public int nextInt() {
            return Integer.parseInt(next());
        }

        public long nextLong() {
            return Long.parseLong(next());
        }

        public double nextDouble() {
            return Double.parseDouble(next());
        }
    }
}