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: Accepted)


local s = io.read()
-- s = "ABCABC"
-- s = "ABCACCBABCBCAABCB"
-- s = "A"
local c = {}
for i = 1, #s do
	c[i] = string.sub(s, i, i)
end
-- print_r(c)

local num = 0
local i = 1
local lastA = 0
while i <= #c - 2 do
	if c[i] == "A" then
		local an = lastA + 1
		local x = i
		for j = i + 1, #c - 2 do
			if c[j] ~= "A" then
				break
			end
			an = an + 1
			x = j
		end
		local bcn = 0
		local k = x + 1
		while k < #c do
			if c[k] == "B" and c[k+1] == "C" then
				bcn = bcn + 1
				k = k + 2
			else
				break
			end
		end
		-- print(222, i, x, k, an, bcn, c[i], c[i+1], c[i+2])
		num = num + an * bcn
		if bcn >= 1 then
			i = k - 1
			c[i] = "A"
			lastA = an - 1
		else
			i = k
			lastA = 0
		end
		-- print_r(c)
		-- print(i)
	else
		i = i + 1
		lastA = 0
	end
end
print(num)