#!/bin/python

n = input()
x1,y1 = map(int,raw_input().split());
f=0
f1=0
for a0 in range(n-1):
    x,y = map(int,raw_input().split());
    if x1==x:
        f+=1;
    if y1==y:
        f1+=1;
    x1=x;
    y1=y;
if f==n-1:
    print "YES"
else:
    if f1==n-1:
        print "YES"
    else:
        print "NO"