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)

import qualified Data.ByteString.Char8 as BS

readString = map BS.unpack . BS.words

getString = readString <$> BS.getLine

searchC :: String -> Int -> Bool
searchC [] n
  | n == 1 = True
  | otherwise = False
searchC (y : ys) n
  | y == 'C' = searchC ys (n + 1)
  | y >= 'a' && y <= 'z' = searchC ys n
  | otherwise = False

main = do
  [s] <- getString
  if head s == 'A' && head (tail s) >= 'a' && head (tail s) <= 'z' && searchC (init (tail s)) 0 && last s >= 'a' && last s <= 'z'
    then putStrLn "AC"
    else putStrLn "WA"