    solve :- say `solve n!'
             to see the moves for "Towers of Hanoi" with n discs;
    solve n = title n ++ hanoi n "A" "B" "C"

    title n = ["TOWERS OF HANOI WITH ",n," DISCS\n"]

    hanoi 0 a b c = []
    hanoi n a b c = hanoi (n - 1) a c b ++ move a b ++ hanoi (n - 1) c b a

    move a b = ["   move disc from ",a," to ",b,nl]
