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

namespace yukicoder_559 {
    class Program {
        static void Main(string[] args) {
            //A:65,B:66
            char[] a = Console.ReadLine().ToCharArray();
            int countB = 0;
            int answer = 0;
            for(int i = 0; i < a.Length; i++) {
                if (a[i] == 66) countB++;
                else answer += countB;
            }
            Console.WriteLine(answer);
            Console.ReadLine();
        }
    }
}