n=int(input())
L=[list(map(str,input().split())) for _ in range(n)]
d=dict()
for a,b in L:
	if a not in d:
		d[a]=1
	else:
		f[a]+=1
	if d[b] not in d:
		d[b]=1
	else:
		d[b]+=1

flag=1
for a,b in L:
	if 1<d[a] and 1<d[b]:
		flag=0
		break
print("Yes" if flag else "No")