from collections import Counter
N = int(input())
Ss = []
Ts = []
C = Counter()
for _ in range(N):
   S, T = input().split()
   Ss.append(S)
   Ts.append(T)
   C[S] += 1
   C[T] += 1


def proc():
   for i in range(N):
      S, T = Ss[i], Ts[i]
      C[S] -= 1
      C[T] -= 1
      if C[S] >= 1 and C[T] >= 1:
         return False
      C[S] += 1
      C[T] += 1
   return True


ans = proc()
print("Yes" if ans else "No")