[ 6:46:43.79] P:\test>MP-FET.pl
8.070604647867604097576877675243109941729476950993498765160880911582E-7030
  1 trial  of _default ( 49.865ms total), 49.865ms/trial

##</code><code>##

cancel (x:xs) (y:ys)
    | x == y    = cancel xs ys
    | x < y     = let (xs', ys') = cancel xs (y:ys) in (x:xs', ys')
    | otherwise = let (xs', ys') = cancel (x:xs) ys in (xs', y:ys')
cancel xs ys    = (xs, ys)