#!/bin/python3

import sys

a = 0
b = 0
i = 0
c = 0
n = int(input().strip())
for a0 in range(n):
    x,y = input().strip().split(' ')
    x,y = [int(x),int(y)]
    if i == 0:
        a = x
        b = y
        i += 1
    
    if a == x or b == y:
        c += 1
    
if c == n:
    print("YES")
else:
    print("NO")