  count = 0
  get_string = gets.chomp
  last_index = get_string.length - 1

  (-(last_index-1)..0).each do |minor_index|
    index = minor_index.abs
    next if get_string[index] == 'W'
    # 右側文字取得
    s = get_string[index + 1 .. last_index]
    # Wの文字数を数える
    count += s.scan(/[W]/).length
  end

  count
