from collections import defaultdict

n = int(input())
st = [list(input().split()) for i in range(n)]

dic = defaultdict(int)

for s,t in st:
	dic[s] += 1
	dic[t] += 1

for s,t in st:
	if dic[s] == 1:
		continue

	if dic[t] == 1:
		continue
	print("No")
	exit()

print("Yes")