n=int(input())
st=[input().split()for _ in range(n)]
for i in range(n):
  s,t=st[i]
  ng=0
  for j in range(n):
    if i==j:
      continue
    if s in st[j]:
      ng|=1
    if t in st[j]:
      ng|=2
  if ng==3:
    exit(print('No'))
print('Yes')