#!/bin/python

import sys

k = []
n = int(raw_input().strip())
for a0 in xrange(n):
    x,y = raw_input().strip().split(' ')
    k.append([int(x),int(y)])
c = True
for i in range(len(k)-1):
    if (k[i][0] != k[i+1][0]) and (k[i][1] != k[i+1][1]):
        c = False
        break
print "YES" if c else "NO"