output_description: Print the string displayed in the editor in the end.
  
  * * *
input_description: The input is given from Standard Input in the following format:
  
      
      
      s
attempt: res = ''
  for x in input():
      if x = 'B':
          res = res[:-1]
      else:
          res += x 
  print(res)
  
  
  
problem_description: Statement
  
  Sig has built his own keyboard. Designed for ultimate simplicity, this
  keyboard only has 3 keys on it: the `0` key, the `1` key and the backspace
  key.
  
  To begin with, he is using a plain text editor with this keyboard. This editor
  always displays one string (possibly empty). Just after the editor is
  launched, this string is empty. When each key on the keyboard is pressed, the
  following changes occur to the string:
  
    * The `0` key: a letter `0` will be inserted to the right of the string.
    * The `1` key: a letter `1` will be inserted to the right of the string.
    * The backspace key: if the string is empty, nothing happens. Otherwise, the rightmost letter of the string is deleted.
  
  Sig has launched the editor, and pressed these keys several times. You are
  given a string s, which is a record of his keystrokes in order. In this
  string, the letter `0` stands for the `0` key, the letter `1` stands for the
  `1` key and the letter `B` stands for the backspace key. What string is
  displayed in the editor now?
samples: [{"input": "01B0", "output": "00\n    \n\nEach time the key is pressed, the string in the editor will change as follows:\n`0`, `01`, `0`, `00`.\n\n* * *"}, {"input": "0BB1", "output": "1\n    \n\nEach time the key is pressed, the string in the editor will change as follows:\n`0`, `(empty)`, `(empty)`, `1`."}]