We're used to doing puzzles which might be mate-in-one (Level I),
mate-in-two (Level II) and so on. Someone asked on Friday, what's
the highest level you can get? Well, I have heard of a 1220-move
monster by Babson, but that has some peculiar conditions.
The most moves in a forced-mate problem with no conditions is this
one, from Otto Blathy, who published a whole book of such
monsters.
Mate in 290 -- best of luck!