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;

fn main() {
    input! {
        s: String,
    }

    let s = s.replace("BC", "D");

    let v = s.chars().collect::<Vec<_>>();

    let mut count = 0;
    let mut a_count = 0;

    for c in v {
        match c {
            'A' => {
                a_count += 1;
            },
            'B'|'C' => {
                a_count = 0;
            },
            'D' => {
                count += a_count;
            },
            _ => {
                unreachable!();
            }
        }
    }

    println!("{}", count);
}