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 Lua (Lua 5.3.5) (judge verdict: Runtime Error)

local str = io.read()
for cur=1, string.len(str) do
	tbl[cur] = string.sub(str,cur,cur)
end
local ans = 0 
local cur = 0	--前两格指针
local charge = false
local cur1 = 0
for i = 1, #tbl do 
	if i > 2 then
		cur = i - 2  
	end
	if tbl[i] == "A" and tbl[i+1] == "B" and tbl[i+2] == "C" then
		ans = ans + 1
		tbl[i] = "B"
		tbl[i+1] = "C"
		tbl[i+2] = "A"
		charge = true
	else
		charge = false
	end
	if charge then 
		while cur > 0 do 
			if tbl[cur] == "A" and tbl[cur+1] == "B" and tbl[cur+2] == "C" then
				ans = ans + 1
				tbl[cur] = "B"
				tbl[cur+1] = "C"
				tbl[cur+2] = "A"
				cur = cur - 2
			else
				cur = 0
			end
		end
	end
end