#!/bin/python

import sys

lastx = None
lasty = None
horizontal = True
vertical = True

n = int(raw_input().strip())
for a0 in xrange(n):
    x,y = raw_input().strip().split(' ')
    x,y = [int(x),int(y)]
    if not ((lastx is None) or (lasty is None)):
        if (vertical):
            vertical = False if (lasty != y) else True
        if (horizontal):
            horizontal = False if (lastx != x) else True
    if (horizontal is False) and (vertical is False):
        print "NO"
        break
    lastx = x
    lasty = y
if (horizontal or vertical):
    print "YES"