#!/bin/python

import sys

yes = 0
xarray = []
yarray = []


n = int(raw_input().strip())
for a0 in xrange(n):
    x,y = raw_input().strip().split(' ')
    x,y = [int(x),int(y)]
    xarray.append(x)
    yarray.append(y)
    
for x in xarray:
    if x == xarray[0]:
        yes +=1
if yes == n:
    print 'YES'
else: 
    yes = 0
    for y in yarray:
        if y == yarray[0]:
            yes +=1
    if yes == n:
        print 'YES'
    else:
        print 'NO'