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