{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE BangPatterns #-}
{-# LANGUAGE TupleSections #-}
{-# LANGUAGE ExplicitForAll #-}
{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE MultiWayIf #-}
{-# LANGUAGE Unsafe #-}

import Data.Bits
import Data.List
import qualified Data.ByteString.Char8 as BS
import qualified Data.ByteString.Lazy.Char8 as BSL
import Data.IntMap.Strict (IntMap)
import qualified Data.IntMap.Strict as IM
import qualified Data.Array.IArray as A
import qualified Data.Array.MArray.Safe as A
-- import qualified Data.Array.MArray as A
import Data.Array (Array)
import Data.Array.Unboxed (UArray)
import Data.Array.IArray (IArray)
import Data.Array.MArray.Safe (MArray)
import Data.Array.IO.Safe (IOArray, IOUArray)
import Data.Array.ST.Safe (STArray, STUArray, runSTArray, runSTUArray)
import qualified Data.Vector.Unboxed as VU
import qualified Data.Vector.Unboxed.Mutable as VUM
import Control.Monad
import Control.Monad.ST
-- import Control.Monad.ST.Safe
import Control.Applicative
import Data.Maybe
import Data.Tuple
import Data.Ord
import Control.Monad.State.Strict
import Data.Int
import System.IO

main :: IO ()
main = do
  xs <- BS.getLine
  let v = VU.map (== 'B') $ VU.unfoldrN (BS.length xs) BS.uncons xs
  print $ query (BS.length xs) v

query :: Int -> VU.Vector Bool -> Int
query s v =
  VU.sum $ VU.map fst $ VU.filter (not . snd) $ VU.zip blackCounts v
  where
    blackCounts :: VU.Vector Int
    blackCounts = VU.prescanl' (flip $ \case{ True -> (+1); _ -> id}) 0 v
