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):
    for family_name, first_name in zip(family_names[index+1:], first_names[index+1:]):
        if family_names[index] == family_name or family_names[index] == first_name:
            for family_name_2, first_name_2 in zip(family_names[index+1:], first_names[index+1:]):
                if first_names[index] == family_name_2 or first_names[index] == first_name_2:
                    answer = "No"
            
print(answer)