n=int(input())
p=[input().split() for _ in range(n)]
呼び方=[]
for i in range(n):
  f=False
  for j in range(n):
    if i==j:
      continue
    if p[i][0]==p[j][0] or p[i][0]==p[j][1]:
      f=True
  if not f:
    呼び方.append(p[i][0])
  else:
    f=False
    for j in range(n):
      if i==j:
        continue
      if p[i][1]==p[j][0] or p[i][1]==p[j][1]:
        f=True
    if not f:
      呼び方.append(p[i][1])
    else:
      exit(print("No"))
print("Yes")