#!/bin/python3

import sys


n = int(input().strip())
points=list()
for a0 in range(n):
    x,y = input().strip().split(' ')
    x,y = [int(x),int(y)]
    points.append((x,y))
    
h=v=True
for i in range(1,n):
    x,y=points[i]
    xo,yo=points[i-1]
    if h:
        if yo!=y:
            h=False
    if v:
        if xo!=x:
            v=False
    if not h and not v:
        print("NO")
        exit(0)
print("YES")