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: Time Limit Exceeded)

package main
import "fmt"
func main() {
  var s string
  fmt.Scan(&s)
  n := len(s)
  x := make([]int,n)
  for i:=0;i<n;i++ {
    if s[i:i+1] == "A" { x[i] = -1 }
    if s[i:i+1] == "C" { x[i] = 1 }
  }
  m := 0
  for i:=1;i<n-1;i++ {
    if x[i-1] == -1 && x[i] == 0 && x[i+1] == 1 {
      x[i-1],x[i],x[i+1] = x[i],x[i+1],x[i-1]
      m++
      i -= 2
      if i < 0 { i = 0 }
    }
  }
  fmt.Println(m)
}