#!/bin/python

import sys

n = int(raw_input().strip())
xs = []
ys = []
for a0 in xrange(n):
    x,y = raw_input().strip().split(' ')
    x,y = [int(x),int(y)]
    xs.append(x)
    ys.append(y)
    
if all([x == xs[0] for x in xs]):
    print "YES"
elif all([x == ys[0] for x in ys]):
    print "YES"
else:
    print "NO"