using System;
using System.Collections.Generic;
using System.IO;

namespace Contest
{
    class Program
    {
        private string S;
        public void Solve()
        {
            var sc = new Scanner();
            S = sc.Next();
            // A BC で分ける
            var list = new List<List<string>>();
            list.Add(new List<string>());
            for (int i = 0; i < S.Length;)
            {
                if (S[i] == 'A')
                {
                    list[list.Count - 1].Add("A");
                    i++;
                }
                else if (S[i] == 'B')
                {
                    if (i + 1 < S.Length && S[i + 1] == 'C')
                    {
                        list[list.Count - 1].Add("BC");
                        i += 2;
                    }
                    else
                    {
                        if (list[list.Count - 1].Count != 0)
                            list.Add(new List<string>());
                        i++;
                    }
                }
                else if (S[i] == 'C')
                {
                    if (list[list.Count - 1].Count != 0)
                        list.Add(new List<string>());
                    i++;
                }
            }

            long ans = 0;

            foreach (List<string> list1 in list)
            {
                long index = 0;
                for (int i = 0; i < list1.Count; i++)
                {
                    if (list1[i] == "BC")
                    {
                        ans += i - index;
                        index++;
                    }
                }
            }
            Console.WriteLine(ans);
        }

        static void Main() => new Program().Solve();
    }
}

class Scanner
{
    public Scanner()
    {
        _stream = new StreamReader(Console.OpenStandardInput());
        _pos = 0;
        _line = new string[0];
        _separator = ' ';
    }
    private char _separator;
    private StreamReader _stream;
    private int _pos;
    private string[] _line;
    #region get a element
    public string Next()
    {
        if (_pos >= _line.Length)
        {
            _line = _stream.ReadLine().Split(_separator);
            _pos = 0;
        }
        return _line[_pos++];
    }
    public int NextInt()
    {
        return int.Parse(Next());
    }
    public long NextLong()
    {
        return long.Parse(Next());
    }
    public double NextDouble()
    {
        return double.Parse(Next());
    }
    #endregion
    #region convert array
    private int[] ToIntArray(string[] array)
    {
        var result = new int[array.Length];
        for (int i = 0; i < array.Length; i++)
        {
            result[i] = int.Parse(array[i]);
        }

        return result;
    }
    private long[] ToLongArray(string[] array)
    {
        var result = new long[array.Length];
        for (int i = 0; i < array.Length; i++)
        {
            result[i] = long.Parse(array[i]);
        }

        return result;
    }
    private double[] ToDoubleArray(string[] array)
    {
        var result = new double[array.Length];
        for (int i = 0; i < array.Length; i++)
        {
            result[i] = double.Parse(array[i]);
        }

        return result;
    }
    #endregion
    #region get array
    public string[] Array()
    {
        if (_pos >= _line.Length)
            _line = _stream.ReadLine().Split(_separator);
        _pos = _line.Length;
        return _line;
    }
    public int[] IntArray()
    {
        return ToIntArray(Array());
    }
    public long[] LongArray()
    {
        return ToLongArray(Array());
    }
    public double[] DoubleArray()
    {
        return ToDoubleArray(Array());
    }
    #endregion
}

Measured memory_bytes: 26208