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: Time Limit Exceeded)

s = gets.chomp

sum = 0
while true
  index = s.index('ABC')
  if index == nil
    break
  end

  a = s[0..index].scan(/A+$/)[0]
  bc_count = s[index+1..s.size].gsub(/^(BC)+/).to_a.first.size / 2
  sum += a.size * bc_count

  s = a + s[(index + bc_count * 2 + 1)...s.size]
end
puts sum