#!/bin/python

import sys

cnt = 0
n = int(raw_input().strip())
for a0 in xrange(n):
	x,y = raw_input().strip().split(' ')
	x,y = [int(x),int(y)]
	if a0 == 0:
		x1 = x
		y1 = y
	if x==x1 or y==y1:
		x1 = x
		y1 = y
	else:
		cnt += 1

if cnt > 0:
	print 'NO'
else:
	print 'YES'