Exchange
In prison, when you have access to a big number of fingers, mouths, and legs you can exchange them for things that are worth more to you. What are you gonna do with all these body parts in prison? You should exchange them for cigarettes and toilet alcohol.
You just have so many fingers, mouths, and legs you've pummeled off of the other prisoners. Exchange them for better loot!
かん
か
None
You learned this type of exchange from the mighty Genghis Khan (かん). You read a book or watched a show about him once and you're pretty positive that Genghis Khan would exchange the body parts of his enemies all over the continents of Asia and Europe for nicer stuff.
Think back to when you were a kid and they would roll out those TVs on stands into the classrooms. Imagine watching a documentary on Genghis Khan's exchange routes where he bought and sold body parts. Educational!