Similarity = # hashes in intersection
             __________________________
             max(total # of hashes in Doc. A, total # of hashes in Doc. B

"Jack and Jill ran up the hill because Jill wanted
to fetch a pail of water. Unfortunately, Jack fell
down and broke his crown. Even worse, Jill came tumbling after."

window 1 = Jack and Jill ran up
window 2 = and Jill ran up the
window 3 = Jill ran up the hill
window 4 = ...