English

Chef is learning English. So far, he knows $N$ words, and he wants to write a verse. Let's call a pair of English words a *stanza*. A *verse* is a list of stanzas. The *prefixal rhyme* of a stanza is the longest common prefix of the words in it. Similarly, the *suffixal rhyme* of a stanza is the longest common suffix of the words in it. The *beauty* of a stanza whose prefixal and suffixal rhyme