指定した位置に'"'を入れる

double_quote.hs

import Control.Applicative
import Control.Monad
import Data.List

main = do
  s <- getLine
  ind <- (map read . words) <$> getLine
  putStrLn $ solve s ind

solve :: String -> [Int] -> String
solve s ind =  init $ concatMap insert_double_quote (zip [0..] (s ++ "_"))
  where insert_double_quote p = (if elem (fst p) ind then ['\"'] else []) ++ [snd p]

{-
waaai
0 2 5
=>
"wa"aai"
-}