output_description: Print the sum of the ABC numbers of all the 3^Q strings, modulo 10^9 + 7.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      S
attempt: import sys, os
  
  f = lambda: list(map(int, input().split()))
  if "local" in os.environ:
      sys.stdin = open("./input.txt", "r")
  
  
  def solve():
      s = input()
      slen = len(s)
      cnt = [0] * 3
      mod = 1000 * 1000 * 1000 + 7
      cnt_q = 0
      for i in range(slen):
          if s[i] == "A":
              cnt[0] += 1
          elif s[i] == "B":
              cnt[1] += cnt[0]
          elif s[i] == "C":
              cnt[2] += cnt[1]
          else:
              cnt[0], cnt[1], cnt[2] = (
                  3 * cnt[0] + 3**cnt_q,
                  3 * cnt[1] + cnt[0],
                  3 * cnt[2] + cnt[1],
              )
              cnt_q += 1
  
          # print(cnt)
  
          cnt[0] %= mod
          cnt[1] %= mod
          cnt[2] %= mod
  
      print(cnt[2])
  
  
  solve()
  
problem_description: Statement
  
  The _ABC number_ of a string T is the number of triples of integers (i, j, k)
  that satisfy all of the following conditions:
  
    * 1 ≤ i < j < k ≤ |T| (|T| is the length of T.)
    * T_i = `A` (T_i is the i-th character of T from the beginning.)
    * T_j = `B`
    * T_k = `C`
  
  For example, when T = `ABCBC`, there are three triples of integers (i, j, k)
  that satisfy the conditions: (1, 2, 3), (1, 2, 5), (1, 4, 5). Thus, the ABC
  number of T is 3.
  
  You are given a string S. Each character of S is `A`, `B`, `C` or `?`.
  
  Let Q be the number of occurrences of `?` in S. We can make 3^Q strings by
  replacing each occurrence of `?` in S with `A`, `B` or `C`. Find the sum of
  the ABC numbers of all these strings.
  
  This sum can be extremely large, so print the sum modulo 10^9 + 7.
samples: [{"input": "A??C", "output": "8\n    \n\nIn this case, Q = 2, and we can make 3^Q = 9 strings by by replacing each\noccurrence of `?` with `A`, `B` or `C`. The ABC number of each of these\nstrings is as follows:\n\n  * `AAAC`: 0\n  * `AABC`: 2\n  * `AACC`: 0\n  * `ABAC`: 1\n  * `ABBC`: 2\n  * `ABCC`: 2\n  * `ACAC`: 0\n  * `ACBC`: 1\n  * `ACCC`: 0\n\nThe sum of these is 0 + 2 + 0 + 1 + 2 + 2 + 0 + 1 + 0 = 8, so we print 8\nmodulo 10^9 + 7, that is, 8.\n\n* * *"}, {"input": "ABCBC", "output": "3\n    \n\nWhen Q = 0, we print the ABC number of S itself, modulo 10^9 + 7. This string\nis the same as the one given as an example in the problem statement, and its\nABC number is 3.\n\n* * *"}, {"input": "????C?????B??????A???????", "output": "979596887\n    \n\nIn this case, the sum of the ABC numbers of all the 3^Q strings is\n2291979612924, and we should print this number modulo 10^9 + 7, that is,\n979596887."}]