import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int x = in.nextInt();
        int y = in.nextInt();
        int prevX = x;
        int prevY = y;
        for (int a0 = 1; a0 < n; a0++){
            x = in.nextInt();
            y = in.nextInt();
            if (x != prevX && y != prevY) {
                System.out.println("NO");
                return;
            }
            prevX = x;
            prevY = y;
        }
        System.out.println("YES");
    }
}