#! /usr/bin/env stack
-- stack --resolver lts-12.20 --install-ghc script
{-# LANGUAGE FlexibleContexts, LambdaCase #-}
module Main where

import Data.Function (fix, on)
import qualified Data.Char as C
import qualified Data.List as L

main :: IO ()
main = interact $ \input -> show $ L.minimumBy (compare `on` snd) $
   [ react $ filter (\c -> C.isAlpha c && c /= r && c /= C.toUpper r) input
   | r <- ['a'..'z']
   ]

react input =
   let scan (x:y:zs) = if x `reactsWith` y then scan zs else (x : scan (y:zs))
       scan zs = zs
       input' = scan input
       result = (input', length input')
   in if input' == input then result else react input'

x `reactsWith` y = (C.isUpper x && C.toLower x == y) ||
                   (C.isLower x && C.toUpper x == y)