import Data.Function (on)
import Data.List (sortBy, groupBy, minimumBy)
import Data.Ord (comparing)
(|>) x f = f x

solve xs ys = 
	let partialSum s (y,x) = s - x *2 + 1 in
	zip ys xs
	|> sortBy (comparing fst)
	|> groupBy (on (==) fst)
	|> scanl (\s x -> (fst s + foldl partialSum 0 x, fst $ head x)) (foldl1 (+) xs, minimum ys - 1)
	|> minimumBy (comparing fst)
	|> snd
	
x1 = [0, 0, 0, 1, 1, 1] 
y1 = [6, 3, 4, 4, 4, 2.1] 
main = print $ solve x1 y1