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 OCaml (4.02.3) (judge verdict: Wrong Answer)

open Batteries
open Printf
let () =
  let s = Scanf.scanf "%s " (fun a -> a) in
  let s1 = String.slice ~last:1 s in
  let s2 = String.slice ~first:2 ~last:(String.length s - 1) s in

  Printf.printf "%s\n" @@
  if s1 = "A" && (
      let l = List.of_enum (
          String.find_all s2 "C"
        )
      in
      List.length l = 1
    )
  then "AC" else "WA"