from collections import Counter

N = int(input())

W_list = []
S_list = []
T_list = []

for _ in range(N):
    S, T = input().split()
    W_list.append(S)
    W_list.append(T)
    
    S_list.append(S)
    T_list.append(T)

W_cnt = Counter(W_list)

for i in range(N):
    S = S_list[i]
    T = T_list[i]
    
    if W_cnt[S] == 1 or W_cnt[T] == 1:
        continue
    else:
        print("No")
        exit()

print("Yes")