#!/bin/python

import sys


n = int(raw_input().strip())
count = 0
is_x = False
is_y = False
for a0 in xrange(n):
    x,y = raw_input().strip().split(' ')
    x,y = [int(x),int(y)]
    if count == 0:
        ex = x
        why = y
    else:
        prev_x = ex
        prev_y = why
        why = y
        ex = x
        
        if prev_x == ex and prev_y != why and is_y is False:
            is_x = True
        elif prev_y == why and prev_x != ex and is_x is False:
            is_y = True
        else:
            is_x = False
            is_y = False
            print 'NO'
            break
    count += 1
if is_x or is_y:
    print 'YES'