Kenneth bought a new phone and added two of his friends' numbers to his phonebook. However, he forgot to transfer the phonebook from his previous phone beforehand. Help Kenneth keep the most up-to-date phone numbers for all his friends on his new device. That is, if there is a number saved on both old and new devices for the same friend, you should keep the number saved on the new phone; or if there is only one phone number for a friend, you should keep it, regardless of which device contains it.