import sys


n = int(raw_input().strip())
x_list = []
y_list = []
for a0 in xrange(n):    
    x,y = raw_input().strip().split(' ')
    x_list.append(int(x))
    y_list.append(int(y))
a = n
tr_fl = 1
while a:
    if x_list[a-1] != int(x):
        tr_fl = 0
        break
    a -= 1
a = n
while a and not tr_fl:
    if y_list[a-1] != int(y):
        tr_fl = 0
        break
    a -= 1
if tr_fl:
    print 'YES'
else:
    print 'NO'