N = int(input())
S, T = [""] * N, [""] * N
for i in range(N):
    S[i], T[i] = input().split()

f = True
for i in range(N):
    s, t = 0, 0
    for j in range(N):
        if i == j: continue
        s |= S[i] == S[j]
        s |= S[i] == T[j]
        t |= T[i] == T[j]
        t |= T[i] == S[j]
    if s & t:
        f = False
    #print(s, t, f)

print("Yes" if f else "No")