AtCoder #003

a.hs

import Control.Applicative

f n xs = (/ n) $ foldr1 (+) $ map g xs where
    g ch | ch == 'A' = 4
         | ch == 'B' = 3
         | ch == 'C' = 2
         | ch == 'D' = 1
         | ch == 'F' = 0

main = do
    n <- read<$>getLine
    xs <- getLine
    print $ f n xs

b.hs

import Data.List 

main = do
    n <- getLine
    xs <- getContents
    putStr $ unlines $ map reverse $ sort $ map reverse $ lines xs