N = int(input())
S = [0] * N
T = [0] * N
for i in range(N):
    S[i], T[i] = input().split()

from collections import Counter

st = S + T

cs = Counter(st)

f = 1
for i in range(N):
    if cs[S[i]] > 1 and cs[T[i]] > 1:
        f = 0
        break

if f == 1:
    print("Yes")
else:
    print("No")