output_description: Print one string with the maximum possible doctoral and postdoctoral quotient
  among the strings that can be obtained by replacing each `?` in T with `P` or
  `D`. If there are multiple such strings, you may print any of them.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      T
attempt: # coding: utf-8
  # Your code here!
  
  #########行列読み込み ##############################################
  """
  from sys import stdin
  n = int(stdin.readline().rstrip())
  data = [stdin.readline().rstrip().split() for _ in range(n)]
  print(data)
  print(*data, sep='\n')
  """
  import itertools
  
  S = input()
  # print(S)
  S_copy = S
  i = S.count("?")
  
  tmp = list(itertools.product(["P", "D"], repeat=i))
  # print(tmp)
  # print(tmp[0])
  num = len(tmp[0])
  ans = []
  for x in range(len(tmp)):
      S = S_copy
      for y in tmp[x]:
  
          S = S.replace("?", y, 1)
          # print(S)
          ans.append(S)
  key = []
  for i in ans:
      # print(type(i))
      # print(type(i.count("PD")))
      key.append(i.count("PD") + i.count("D"))
  # print(key)
  d = dict(zip(ans, key))
  # print(d)
  max_k = max(d, key=d.get)
  print(max_k)
  
problem_description: Statement
  
  For a string S consisting of the uppercase English letters `P` and `D`, let
  the _doctoral and postdoctoral quotient_ of S be the total number of
  occurrences of `D` and `PD` in S as contiguous substrings. For example, if S =
  `PPDDP`, it contains two occurrences of `D` and one occurrence of `PD` as
  contiguous substrings, so the doctoral and postdoctoral quotient of S is 3.
  
  We have a string T consisting of `P`, `D`, and `?`.
  
  Among the strings that can be obtained by replacing each `?` in T with `P` or
  `D`, find one with the maximum possible doctoral and postdoctoral quotient.
samples: [{"input": "PD?D??P", "output": "PDPDPDP\n    \n\nThis string contains three occurrences of `D` and three occurrences of `PD` as\ncontiguous substrings, so its doctoral and postdoctoral quotient is 6, which\nis the maximum doctoral and postdoctoral quotient of a string obtained by\nreplacing each `?` in T with `P` or `D`.\n\n* * *"}, {"input": "P?P?", "output": "PDPD"}]