#!/bin/python

import sys

contx=0
conty=0

z,t=None,None
n = int(raw_input().strip())
for a0 in xrange(n):
    x,y = raw_input().strip().split(' ')
    x,y = [int(x),int(y)]
 
    if a0==0:
        z,t=x,y
        contx+=1
        conty+=1
       # print x,y,z,t
    else:
        if x==z:
            contx+=1
            z,t=x,y
            #print x,y,z,t
            
        elif y==t:
            conty+=1
            z,t=x,y
           # print x,y,z,t
        
if contx==n or conty==n:
    print 'YES'
else:
    print 'NO'