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 Go (1.6) (judge verdict: Accepted)

package main

import (
	"bytes"
	"fmt"
)

func main() {
	var s []byte
	fmt.Scan(&s)

	s = bytes.Replace(s, []byte("BC"), []byte("D"), -1)
	ans := 0
	ctA := 0
	for i := 0; i < len(s); i++ {
		switch s[i] {
		case 'A':
			ctA++
		case 'D':
			ans += ctA
		default:
			ctA = 0
		}
	}

	fmt.Println(ans)
}