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 (
	"fmt"
)

func main() {
	var s string
	fmt.Scan(&s)

	var i int
	var ret int
	var aSeq int
	for i < len(s)-2 {
		if s[i:i+3] == "ABC" {
			ret += aSeq + 1
			s = "A" + s[i+3:]
			i = 0
		} else {
			if s[i] == 'A' {
				aSeq++
			} else {
				aSeq = 0
			}
			i++
		}
	}
	fmt.Println(ret)
}