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 scanner = new Scanner(System.in);
        int indexLength = scanner.nextInt();
        int[] xValues = new int[indexLength];
        boolean horz = true;
        for(int indexOne = 0; indexOne < indexLength; indexOne++){
            int x = scanner.nextInt();
            for (int indexTwo = 0; indexTwo < indexOne; indexTwo++) {
                if (x != xValues[indexTwo]) {
                    horz = false;
                }
                xValues[indexOne] = x;
            }
            int y = scanner.nextInt();
        }
        
        if (horz) {
            System.out.println("YES");
        } else {
            System.out.println("NO");
        }
    }
}