Problem:
Score : 600 points

Problem Statement

You are given a string s consisting of A, B and C.

Snuke wants to perform the following operation on s as many times as possible:

Choose a contiguous substring of s that reads ABC and replace it with BCA.

Find the maximum possible number of operations.

Constraints

1 \leq |s| \leq 200000

Each character of s is A, B and C.

Input

Input is given from Standard Input in the following format:

s

Output

Find the maximum possible number of operations.

Sample Input 1

ABCABC

Sample Output 1

3

You can perform the operations three times as follows: ABCABC → BCAABC → BCABCA → BCBCAA. This is the maximum result.

Sample Input 2

C

Sample Output 2

0

Sample Input 3

ABCACCBABCBCAABCB

Sample Output 3

6

Solution in C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;

namespace BABC
{
    class Program
    {
        static void Main(string[] args)
        {
            // 入力の取得
            var s = Console.ReadLine().ToCharArray();

            var answer = 0;
            int countA = 0, index = 0;
            while (index < s.Length - 1)
            {
                switch (s[index])
                {
                    case 'A' :
                        countA++;
                        break;
                    case 'B' :
                        if (s[index + 1] == 'C')
                        {
                            answer += countA;
                            index++;
                        }
                        else
                        {
                            countA = 0;
                        }
                        break;
                    case 'C' :
                        countA = 0;
                        break;
                }

                index++;
            }

            // 解答の出力
            Console.WriteLine(answer);
        }
    }
}