#input of int(split by space)
def get_i()
  return gets.chomp.split(" ").map(&:to_i)
end
#input of float(split by space)
def get_f()
  return gets.chomp.split(" ").map(&:to_f)
end
#input of string(split by space)
def get()
  return gets.chomp.split(" ")
end
#input of string(split per one character)
def get_nsp()
  return gets.chomp.split("")
end
#yes or no decision
def yn_judge(bool,y="Yes",n="No")
  return bool ? y : n 
end
#create of array
def array(size1,init=nil,size2=-1)
  if size2==-1
      return Array.new(size1){init}
  else
      return Array.new(size2){Array.new(size1){init}}
  end
end

def max(a,b)
    return a>b ? a : b
end

def min(a,b)
    return a>b ? b : a
end

INF=Float::INFINITY

S=get_nsp
N=S.size
i=0
t=[]
ans=0
while i<N
  if S[i]=="B" and S[i+1]=="C"
      t.push("BC")
      i+=2
  elsif S[i]=="A"
      t.push("A")
      i+=1
  else
      bc=0
      t.each_with_index do|c,i|
        if c=="BC"
          ans+=i-bc
          bc+=1  
        end
      end
      t=[]
      i+=1
  end
end
if t!=[]
      bc=0
      t.each_with_index do|c,i|
        if c=="BC"
          ans+=i-bc
          bc+=1  
        end
      end
      t=[]
      i+=1

end
puts ans