#!/bin/python3

import sys

_x = None
_y = None
vertical_line = True
horizontal_line = True
same_line = True

n = int(input().strip())
for a0 in range(n):
    x,y = input().strip().split(' ')
    x,y = [int(x),int(y)]
    
    if not _x or not _y:
        _x, _y = x, y
    
    if (_x != x and _y != y):
        same_line = False
    elif (x != x) and horizontal_line:
        vertical_line = False
    elif (y != y) and vertical_line:
        horizontal_line = False
        
if same_line:
    print("YES")
else:
    print("NO")