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

namespace YukiCoder
{
    class Program
    {
        static void Main(string[] args)
        {
            var va = Console.ReadLine();
            int[] pn = new int[va.Length];
            int sum = 0;
            for (int i = 0, j = 0; i < va.Length; i++)
            {
                if (va[i] == 'A') sum += i - j++;
            }
            Console.WriteLine(sum);
            Console.ReadLine();
        }
    }
}