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;


namespace AtC
{
    class Program
    {
        static void Main(string[] args)
        {
            Out(Regex.IsMatch(ReadString(), "^A[a-z]+C[a-z]+$") ? "AC" : "WA");
        }

        //最小公倍数
        static int LCM(int num1, int num2)
        {
            var gcd = GCD(num1, num2);
            return num1 * (num2 / gcd);
        }

        static long LCM(long num1, long num2)
        {
            var gcd = GCD(num1, num2);
            return num1 * (num2 / gcd);
        }

        //最大公約数
        static int GCD(int num1, int num2)
        {
            int a = Math.Max(num1, num2);
            int b = Math.Min(num1, num2);
            int mod;
            while ((mod = a % b) != 0)
            {
                a = b;
                b = mod;
            }

            return b;
        }

        static long GCD(long num1, long num2)
        {
            long a = Math.Max(num1, num2);
            long b = Math.Min(num1, num2);
            long mod;
            while ((mod = a % b) != 0)
            {
                a = b;
                b = mod;
            }

            return b;
        }

        static int[] ReadIntArray()
        {
            return Console.ReadLine().Split(' ').Select(int.Parse).ToArray();
        }

        static int ReadInt()
        {
            return int.Parse(Console.ReadLine());
        }

        static long[] ReadLongArray()
        {
            return Console.ReadLine().Split(' ').Select(long.Parse).ToArray();
        }

        static long ReadLong()
        {
            return long.Parse(Console.ReadLine());
        }

        static string ReadString()
        {
            return Console.ReadLine();
        }

        static void Out(object o)
        {
            Console.WriteLine(o);
        }
    }

    static class EnumerableExtension
    {
        public delegate void Function<in T>(T val);

        public static void ForEach<T>(this IEnumerable<T> enumerable, Function<T> function)
        {
            foreach (var x in enumerable)
            {
                function(x);
            }
        }
    }

    class PriorityQueue<T>
    {
        private readonly List<Tuple<int, T>> _list = new List<Tuple<int, T>>();

        public PriorityQueue()
        {
        }

        public void Push(T item, int priority)
        {
            var itemIndex = _list.Count;
            _list.Add(Tuple.Create(priority, item));
            int parentIndex;
            while ((parentIndex = GetParentIndex(itemIndex)) != -1 && priority > _list[parentIndex].Item1)
            {
                Swap(itemIndex, parentIndex);
                itemIndex = parentIndex;
            }
        }

        private int GetParentIndex(int index)
        {
            if (index == 0) return -1;
            return ((index + 1) >> 1) - 1;
        }

        private Tuple<int, int> GetChildrenIndex(int index)
        {
            var item2 = (index + 1) << 1;
            var item1 = item2 - 1;
            return item2 >= _list.Count ? null : Tuple.Create(item1, item2);
        }

        public T Pop()
        {
            var item = _list[0].Item2;
            Tuple<int, int> childrenIndex;
            int index = 0;
            while ((childrenIndex = GetChildrenIndex(index)) != null)
            {
                if (_list[childrenIndex.Item1].Item1 > _list[childrenIndex.Item2].Item1)
                    _list[index] = _list[childrenIndex.Item1];
                else
                    _list[index] = _list[childrenIndex.Item2];
            }

            return item;
        }

        public T Peek()
        {
            return _list[0].Item2;
        }

        private void Swap(int index1, int index2)
        {
            var tmp = _list[index1];
            _list[index1] = _list[index2];
            _list[index2] = tmp;
        }
    }

    class UnionFind
    {
        private readonly int[] _array;

        public UnionFind(int N)
        {
            _array = new int[N];
            for (int i = 0; i < N; i++)
            {
                _array[i] = i;
            }
        }

        public int GetRootNode(int n)
        {
            if (_array[n] == n) return n;
            return _array[n] = GetRootNode(_array[n]);
        }

        public void UnionGroup(int a, int b)
        {
            var rootA = GetRootNode(a);
            var rootB = GetRootNode(b);
            if (rootA == rootB) return;
            _array[rootA] = rootB;
        }

        public bool IsSameGroup(int a, int b) => GetRootNode(a) == GetRootNode(b);

        public bool IsRoot(int n) => _array[n] == n;
    }
}