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: Accepted)

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

  # 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

  for m in eachmatch(r"[AD]+", s)
    ss=m.match
    l=length(ss)
    ix=(1:l)[collect(ss).=='A']
    k=length(ix)
    n+=sum(l-ix)-div((k-1)*k,2)
  end

  n |> println
end

main()