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 Julia (0.5.0) (judge verdict: Time Limit Exceeded)

parseInt(x) = parse(Int, x)
parseArray(x::Array{SubString{String}, 1}) = map(parseInt, x)

function main()
  s = readline() |> strip

  s=replace(s, "BC", "D")
  n=0

  # for ss in eachmatch(r"A|D", s)
  # end

  while true
    nn=0
    a=collect(s)
    for m in eachmatch(r"AD", s)
      i=m.offset
      a[i],a[i+1]=a[i+1],a[i] # "AD" -> "DA"
      nn+=1
    end
    nn==0 && break
    n+=nn
    s=join(a)
  end

  n |> println
end

main()