n=int(input())
s,t=['']*n,['']*n
for i in range(n):
 s[i],t[i]=input().split()
flag=True
for i in range(n):
 u,v=0,0
 for j in range(n):
  if i==j:
   continue
  u|=s[i]==s[j]
  u|=s[i]==t[j]
  v|=t[i]==t[j]
  v|=t[i]==s[j]
 if u&v:
  flag=False
print('Yes' if flag else 'No')