from collections import defaultdict


N = int(input())
cnt = defaultdict(int)
S, T = [], []
for _ in range(N):
    s, t = input().split()
    S.append(s)
    T.append(t)
    cnt[s] += 1
    cnt[t] += 1
for s, t in zip(S, T):
    if cnt[s] == 1 or cnt[t] == 1:
        continue
    print('No')
    exit()

print('Yes')