
local str = io.read()
local ans = 0
local tbl = {}
for cur=1, string.len(str) do
	tbl[cur] = string.sub(str,cur,cur)
end

local cur = 1
while cur< #tbl 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"
		l = cur -1 
		while l > 0 and tbl[l] == "A" do
			ans = ans + 1
			l = l - 1
		end
	end
   cur = cur+1
end
print(ans)