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 C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;
using Console = System.Console;

namespace Atcoder
{
    class Program
    {
        static void Main(string[] args)
        {
            var S = Console.ReadLine();

            // 条件を順番に潰していく。
            // WAの条件に引っかかった時点で出力し、最後まで残ったものがACになる。

            // Aから始まるか判定
            if (!S.StartsWith("A"))
            {
                Console.WriteLine("WA");
                return;
            }

            // 3文字目と末尾から2文字目の間にCがあるか判定
            var tmp = S.Substring(2, S.Length - 3);
            if (tmp.Where(x => x == 'C').ToList().Count != 1)
            {
                Console.WriteLine("WA");
                return;
            }

            // 3文字目と末尾から2文字目に存在する大文字Cの位置を求める
            var cindex = tmp.IndexOf('C') + 2;

            // AとCを消す
            S = S.Remove(cindex, 1).Remove(0, 1);

            // AとCを消した後の文字列に大文字が含まれるか判定
            foreach (var item in S)
            {
                if (char.IsUpper(item))
                {
                     Console.WriteLine("WA");
                     return;
                }
            }

            Console.WriteLine("AC");
        }
    }
}