#!/bin/python

import sys


n = int(raw_input().strip())
l=[]
m=[]
for a0 in xrange(n):
    x,y = map(int, raw_input().split())
    l.append(x)
    m.append(y)
if l.count(l[0])==n or m.count(m[0])==n:
        print "YES";
else:
        print "NO"