#!/bin/python

import sys
h = True
v = True

n = int(raw_input().strip())
for a0 in xrange(n):
    x,y = raw_input().strip().split(' ')
    if a0!=0:
        if x!=xprev:
            v = False
        if y!=yprev:
            h = False
        if not v and not h:
            break
    xprev = x
    yprev = y
print "YES" if v or h else "NO"