/*
csc -debug B.cs && mono --debug B.exe <<< "AABCAABC"
-> 6

csc -debug B.cs && mono --debug B.exe <<< "ABCAABCAABC"
-> 9
*/

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Reflection;

public class HelloWorld {
    public static void SolveCodeForces() {
        var S = Console.ReadLine();
        var n = S.Length;

        if (n == 0) {
            System.Console.WriteLine(0);
            return;
        }

        var A = new List<char>();
        for (var i = 0; i < n; i++) {
            if (S[i] == 'B' && i < n-1 && S[i+1] == 'C') {
                A.Add('D');
                i++;
            }
            else
                A.Add(S[i]);
        }

        n = A.Count;

// System.Console.WriteLine(string.Join(" ", A));

        var ans = 0L;
        var start = -1;
        for (var i = 0; i <= n; i++) {
            if (i == n || (A[i] != 'A' && A[i] != 'D')) {
                var curr = 0L;

                var cnt = 0L;
                for (var j = start+1; j < i; j++) {
                    if (A[j] == 'D') {
                        curr += (long)j - (start + 1) - cnt;
                        cnt++;
                    }
                }

// System.Console.WriteLine(new {start, i, cnt, curr});

                ans += curr;

                start = i;
            }
        }

        System.Console.WriteLine(ans);
    }

    static Scanner cin = new Scanner();
    static StringBuilder cout = new StringBuilder();

    static public void Main () {
        SolveCodeForces();
        // IncreaseStack(SolveCodeForces);
        // System.Console.Write(cout.ToString());
    }

    public static void IncreaseStack(ThreadStart action, int stackSize = 128000000)
    {
        var thread = new Thread(action, stackSize);
        thread.Start();
        thread.Join();
    }
}

public static class Helpers {
    public static T[] CreateArray<T>(int length, Func<int, T> itemCreate) {
        var result = new T[length];
        for (var i = 0; i < result.Length; i++)
            result[i] = itemCreate(i);
        return result;
    }
}

public class Scanner
{
    private string[] line = new string[0];
    private int index = 0;

    public string Next() {
        if (line.Length <= index) {
            line = Console.ReadLine().Split(' ');
            index = 0;
        }
        var res = line[index];
        index++;
        return res;
    }

    public int NextInt() {
        return int.Parse(Next());
    }

    public long NextLong() {
        return long.Parse(Next());
    }

    public ulong NextUlong() {
        return ulong.Parse(Next());
    }

    public string[] Array() {
        line = Console.ReadLine().Split(' ');
        index = line.Length;
        return line;
    }

    public int[] IntArray(int emptyPrefixLen = 0) {
        var array = Array();
        var result = new int[emptyPrefixLen + array.Length];
        for (int i = 0; i < array.Length; i++)
            result[emptyPrefixLen + i] = int.Parse(array[i]);
        return result;
    }

    public long[] LongArray() {
        var array = Array();
        var result = new long[array.Length];
        for (int i = 0; i < array.Length; i++)
            result[i] = long.Parse(array[i]);
        return result;
    }

    public ulong[] UlongArray() {
        var array = Array();
        var result = new ulong[array.Length];
        for (int i = 0; i < array.Length; i++)
            result[i] = ulong.Parse(array[i]);
        return result;
    }
}

Measured memory_bytes: 13212