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 Ruby (2.3.3) (judge verdict: Wrong Answer)

s = gets.chomp.chars

n = s.length
ans = 0
a_cnt = 0
b_flag = false

n.times do |i|
  if s[i] == 'A'
    a_cnt += 1
    b_flag = false
  end

  if s[i] == 'B'
    b_flag = true
  end

  if s[i] == 'C'
    unless b_flag
      a_cnt = 0
      next
    end
    
    ans += a_cnt
    b_flag = false
  end
end

puts ans