#!/bin/python3

import sys
    
n = int(input().strip())
x0,y0 = input().strip().split(' ')
x0,y0 = [int(x0), int(y0)]
f = 'xy'
f2 = 1
for a0 in range(n-1):
    x,y = input().strip().split(' ')
    x,y = [int(x),int(y)]
    if f == 'x':
        if x != x0:
            f2 = 0
            break
    elif f == 'y':
        if y != y0:
            f2 = 0
            break
    elif f == 'xy':
        if x != x0 and y != y0:
            f2 = 0
            break
        elif x != x0:
            f = 'y'
        elif y != y0:
            f = 'x'
            
if f2:
    print("YES")
else:
    print("NO")