#!/bin/python

import sys

listy=[]
counter=0
n = int(raw_input().strip())
for a0 in xrange(n):
    x,y = raw_input().strip().split(' ')
    listy.append([int(x),int(y)])
for a1 in range(n-1):
    if (listy[a1][0]==listy[a1+1][0]):
        counter+=1
    elif (listy[a1][1]==listy[a1+1][1]):
        counter+=1       
if counter==len(listy)-1:
    print "YES"
else:
    print "NO"