Problem:
Score : 200 points

Problem Statement

You are given a string S. Each character of S is uppercase or lowercase English letter.
Determine if S satisfies all of the following conditions:

The initial character of S is an uppercase A.

There is exactly one occurrence of C between the third character from the beginning and the second to last character (inclusive).

All letters except the A and C mentioned above are lowercase.

Constraints

4 ≤ |S| ≤ 10 (|S| is the length of the string S.)

Each character of S is uppercase or lowercase English letter.

Input

Input is given from Standard Input in the following format:

S

Output

If S satisfies all of the conditions in the problem statement, print AC; otherwise, print WA.

Sample Input 1

AtCoder

Sample Output 1

AC

The first letter is A, the third letter is C and the remaining letters are all lowercase, so all the conditions are satisfied.

Sample Input 2

ACoder

Sample Output 2

WA

The second letter should not be C.

Sample Input 3

AcycliC

Sample Output 3

WA

The last letter should not be C, either.

Sample Input 4

AtCoCo

Sample Output 4

WA

There should not be two or more occurrences of C.

Sample Input 5

Atcoder

Sample Output 5

WA

The number of C should not be zero, either.

Solution in Haskell (GHC 7.10.3) (judge verdict: Accepted)

module Main where

import           Data.Char (isLower, isUpper)
import Text.ParserCombinators.ReadP (ReadP, char, satisfy, many, eof, readP_to_S)
import Control.Monad.State
import Data.List (delete)

parser :: ReadP ()
parser = char 'A' *> lowerChar *> many lowerChar *> char 'C' *> many lowerChar *> lowerChar *> eof
-- parser = char 'A' *> many1 lowerChar *> char 'C' *> many1 lowerChar *> eof

lowerChar :: ReadP Char
lowerChar = satisfy isLower

f :: String -> Result
f s = if not . null . readP_to_S parser $ s then AC else WA

main :: IO ()
-- main = interact $ show . f
main = print . f =<< getLine

data Result
  = AC
  | WA
  deriving (Show, Eq)

-- f :: String -> Result
-- f s = if isHeadA s && containsC s && isRemainLower s then AC else WA

isHeadA :: String -> Bool
isHeadA ('A' : _) = True
isHeadA _         = False

containsC :: String -> Bool
containsC = (1 ==) . length . filter ('C' ==) . init . drop 2

isRemainLower :: String -> Bool
isRemainLower = all isLower . remain

remain :: String -> String
remain s =
  -- filter (`notElem` "AC") s
  delete 'A' $ delete 'C' s

  -- let
  --   middle = filter ('C' /=) . init . drop 2
  -- in
  --   (s !! 1 : middle s) ++ [last s]

tests :: [Bool]
tests =
  [ test1
  , test2
  , test3
  , test4
  , test5
  ]

test1, test2, test3, test4, test5 :: Bool
test1 = f "AtCoder" == AC
test2 = f "ACoder" == WA
test3 = f "AcycliC" == WA
test4 = f "AtCoCo" == WA
test5 = f "Atcoder" == WA

-- f :: String -> Result
-- f s = runState (mapM (g (length s)) $ zip [0..] s) 0

-- g :: Int -> (Int, Char) -> State Int Bool
-- g l (0, c)
--   | c /= 'A' = return False
-- g l (i, c)
--   | isUpper c = do
--     if i == 0 || i == l - 1 || c /= 'C'
--       then return False
--       else modify succ

-- g _ _ = return True