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: import sys
  import math
  import collections
  import itertools
  import array
  import inspect
  
  # Set max recursion limit
  sys.setrecursionlimit(1000000)
  
  
  # Debug output
  def chkprint(*args):
      names = {id(v): k for k, v in inspect.currentframe().f_back.f_locals.items()}
      print(", ".join(names.get(id(arg), "???") + " = " + repr(arg) for arg in args))
  
  
  # Binary converter
  def to_bin(x):
      return bin(x)[2:]
  
  
  def li_input():
      return [int(_) for _ in input().split()]
  
  
  def gcd(n, m):
      if n % m == 0:
          return m
      else:
          return gcd(m, n % m)
  
  
  def gcd_list(L):
      v = L[0]
  
      for i in range(1, len(L)):
          v = gcd(v, L[i])
  
      return v
  
  
  def lcm(n, m):
      return (n * m) // gcd(n, m)
  
  
  def lcm_list(L):
      v = L[0]
  
      for i in range(1, len(L)):
          v = lcm(v, L[i])
  
      return v
  
  
  # Width First Search (+ Distance)
  def wfs_d(D, N, K):
      """
      D: 隣接行列(距離付き)
      N: ノード数
      K: 始点ノード
      """
  
      dfk = [-1] * (N + 1)
      dfk[K] = 0
  
      cps = [(K, 0)]
      r = [False] * (N + 1)
      r[K] = True
      while len(cps) != 0:
          n_cps = []
          for cp, cd in cps:
              for i, dfcp in enumerate(D[cp]):
                  if dfcp != -1 and not r[i]:
                      dfk[i] = cd + dfcp
                      n_cps.append((i, cd + dfcp))
                      r[i] = True
  
          cps = n_cps[:]
  
      return dfk
  
  
  # Depth First Search (+Distance)
  def dfs_d(v, pre, dist):
      """
      v:  現在のノード
      pre: １つ前のノード
      dist: 現在の距離
  
      以下は別途用意する
      D: 隣接リスト(行列ではない)
      D_dfs_d: dfs_d関数で用いる，始点ノードから見た距離リスト
      """
  
      global D
      global D_dfs_d
  
      D_dfs_d[v] = dist
  
      for next_v, d in D[v]:
          if next_v != pre:
              dfs_d(next_v, v, dist + d)
  
      return
  
  
  def sigma(N):
      ans = 0
      for i in range(1, N + 1):
          ans += i
      return ans
  
  
  def comb(n, r):
      if n - r < r:
          r = n - r
      if r == 0:
          return 1
      if r == 1:
          return n
  
      numerator = [n - r + k + 1 for k in range(r)]
      denominator = [k + 1 for k in range(r)]
  
      for p in range(2, r + 1):
          pivot = denominator[p - 1]
          if pivot > 1:
              offset = (n - r) % p
              for k in range(p - 1, r, p):
                  numerator[k - offset] /= pivot
                  denominator[k] /= pivot
  
      result = 1
      for k in range(r):
          if numerator[k] > 1:
              result *= int(numerator[k])
  
      return result
  
  
  def bisearch(L, target):
      low = 0
      high = len(L) - 1
  
      while low <= high:
          mid = (low + high) // 2
          guess = L[mid]
          if guess == target:
              return True
          elif guess < target:
              low = mid + 1
          elif guess > target:
              high = mid - 1
      if guess != target:
          return False
  
  
  # --------------------------------------------
  
  dp = None
  
  
  def main():
      S = input()
      R = ""
  
      for s in S:
          if s == "B":
              if len(R) >= 1:
                  R = R[:-1]
          else:
              R += s
  
      print(R)
  
  
  main()
  
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`."}]