#!/bin/python3

import sys


n = int(input().strip())
lst = []
for a0 in range(n):
    x,y = input().strip().split(' ')
    x,y = [int(x),int(y)]
    lst.append((x,y))
ans, c, ind = True, 0, 0
if (lst[0][0] == lst[1][0]):
    c, ind = lst[0][0], 0
elif(lst[0][1] == lst[1][1]):
    c, ind = lst[0][1], 1
else: 
    ans = False
for i in range(2, len(lst)):
    if (lst[i][ind] != c):
        ans = False
if(ans):
    print("YES")
else:
    print("NO")