N = int(input())

dic = {}

S = []
T = []

for i in range(N):

    s,t = input().split()

    if s not in dic:
        dic[s] = 0
    dic[s] += 1

    if t not in dic:
        dic[t] = 0
    dic[t] += 1

    S.append(s)
    T.append(t)

ans = "Yes"
for s,t in zip(S,T):

    if dic[s] == 1 or dic[t] == 1:
        pass
    else:
        ans = "No"
        break

print (ans)