#!/bin/python import sys n = int(raw_input().strip()) a = [] for i in range(n): x = map(int,raw_input().split(' ')); a.append(x) count = 0 count2 = 0 if(n>1): if(a[0][0] == a[1][0]): for i in range(2,n): if(a[i][0] == a[0][0]): count +=1 continue else: print 'NO' break i+=1 elif(a[0][1] == a[1][1]): for i in range(2,n): if(a[i][1] == a[0][1]): count +=1 continue else: print 'NO' break i+=1 else: print "NO" count2 = -1 if(count == n-2 and count2 != -1):print "YES" else: print "YES"