n = int(input())
family_names = []
first_names = []
for _ in range(n):
    s, t = map(str, input().split())
    family_names.append(s)
    first_names.append(t)

answer = "Yes"
for index in range(n):
    family_name_flag = True
    first_name_flag = True
    for index_2 in range(n):
        if index == index_2:
            continue
        if family_names[index] == family_names[index_2] or family_names[index] == first_names[index_2]:
            family_name_flag = False
        if first_names[index] == first_names[index_2] or first_names[index] == family_names[index_2]:
            first_name_flag = False
    if family_name_flag == False and first_name_flag == False:
        answer = "No"
    
            
print(answer)