#!/bin/python

import sys


n = int(raw_input().strip())
x=[]
y=[]
for a0 in xrange(n):
    a,b = map(int,raw_input().split(" "))
    x.append(a)
    y.append(b)
z=x[0]
s=y[0]
if x.count(z) == n :
    print "YES"
elif y.count(s) == n :
    print "YES"
else:
    print "NO"