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by Martin DeMello

In Scrabble parlance, a 'bingo stem' is defined as a set of six
letters that combines with a large fraction of the alphabet to anagram
to valid seven letter words (a 'bingo' is a move using all seven tiles
on your rack). For instance, one of the more prolific stems, SATIRE,
combines with twenty letters, A, B, C, D, E, F, G, H, I, K, L, M, N,
O, P, R, S, T, V, W (forming words like ASTERIA, BAITERS, RACIEST
...).

Write a program that, given a word list and a cutoff n, finds all 6
letter stems that combine with n or more letters, sorted in order of
how many distinct letters they combine with.