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 Rust (1.42.0) (judge verdict: Wrong Answer)

use proconio::input;
use proconio::marker::Chars;

fn main() {
    input! {
        s: Chars
    };
    let n = s.len();
    let mut t = vec![];
    let mut i = 0;
    while i < n {
        if s[i] == 'B' && i + 1 < n && s[i + 1] == 'C' {
            t.push('D');
            i += 2;
        } else {
            t.push(s[i]);
            i += 1;
        };
    }
    let mut c = 0;
    let mut c_a = 0;
    for &t_i in t.iter() {
        match t_i {
            'A' => {
                c_a += 1;
            }
            'D' => {
                c += c_a;
            }
            _ => {
                c_a = 0;
            }
        }
    }
    println!("{}", c);
}