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 PHP7 (7.0.15) (judge verdict: Accepted)

<?php
ini_set('error_reporting', E_ALL & ~E_NOTICE);
fscanf(STDIN, "%s", $S);
$S = str_replace("BC", "D", $S);
$len = strlen($S);
$ans = 0;
$cnt = $streak = 0;
$streak = 0;
for ($i = 0; $i < $len; $i++) {
    if ($S[$i] === 'A' || $S[$i] === 'D') {
        $streak++;
        if ($S[$i] === 'A') {
            $cnt++;
        } else {
            $ans += $cnt;
        }
    } else {
        $cnt = $streak = 0;
    }
}
echo $ans;