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: Time Limit Exceeded)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace AGC034B
{
    class Program
    {
        static int counter = 0;
        static void Main(string[] args)
        {
            string s = Console.ReadLine();

            changeABC(s);
            Console.WriteLine(counter);
        }
        static string changeABC(string s)
        {
            string[] del = { "ABC" };
            string[] ans = s.Split(del, StringSplitOptions.None);
            string result_S = string.Join("", ans);
            string result = string.Join("BCA", ans);
            if (s.Length - result_S.Length>0)
            {
                counter += (s.Length - result_S.Length) / 3;
                changeABC(result);
            }
            return result;
        }
    }
}