#!/bin/python

import sys


n = int(raw_input().strip())

x,y = raw_input().strip().split(' ')
x0,y0 = [int(x),int(y)]
v = False
h = False

for a0 in xrange(n-1):
    x,y = raw_input().strip().split(' ')
    x,y = [int(x),int(y)]
    if a0 == 0:
        if x0 == x:
            v = True
        elif  y0 == y:
            h = True
        else:
            print('NO')
            break
    else:
        if h:
            if y != y0:
                print('NO')
                break
        if v:
            if x != x0:
                print('NO')
                break
    if a0 == n-2:
        print('YES')