A sign-up system exports its accounts as a list accounts. Each account is a list of strings: the first is the owner's name, and the rest are the account's email addresses, at least one.

Two accounts belong to the same person when they share an email, and sharing chains: if account 0 shares an email with account 1, and account 1 shares a different email with account 2, all three are one person. Two people can have the same name, so a matching name proves nothing. All accounts of one person carry the same name. An email can appear in several accounts, and even twice in one account.

Return one list per person: the name, then every email of that person once, in sorted order (the order Python's sorted gives). The people can come in any order.