#!/bin/python

import sys


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:
        p, q = x, y
        continue
    if (p != x) and (q != y):
        print "NO"
        sys.exit()
print "YES"