The Imperfect Sheet

Being bored with the traps in your secret hideout design, you decided to go for something classical, but always enjoyable - the spinning blade. You ordered a really heavy metal sheet out of which you will cut the blade; a uniform square C-by-R grid will be painted on the sheet. You have determined the best shape for the blade -- you will first cut a large square consisting of K-by-K grid cells, wh