T=int(raw_input(''))
T_copy=T
A=[]
while T:
    T-=1
    x,y=map(int,raw_input('').split(' '))
    A.append((x,y))
answer=True
for i in range(T_copy-1):
    if A[i][0]!=A[i+1][0]:
        answer=False
        break
if not answer:
    answer=True
    for i in range(T_copy-1):
        if A[i][1]!=A[i+1][1]:
            answer=False
            break
if answer:
    print 'YES'
else:
    print 'NO'