output_description: Print the number of ways to select cards such that the average of the written
  integers is exactly A.
  
  * * *
input_description: The input is given from Standard Input in the following format:
  
      
      
      N A
      x_1 x_2 ... x_N
attempt: n, a = map(int,input().split())
  x = list(map(int,input().split()))
  
  xx = []
  for i in range(n):
      xx.append(x-a)
  X = max(xx)    
  #dp
  def dp(j,t,l=xx):
      if j = 0 and t = n * X:
          return 1
      elif j > 0 and t -l[j] < 0 or t- l[j] > 2* n * X:
          return dp(j-1,t,l=xx)
      elif j > 1 and 0 <= t-l[j] <= 2*n*X:
          return dp(j-1,t,l = xx) + dp(j-1,t-l[j],l = xx)
      else:
          return 0
      
  print(dp(n,n*X,l=xx) - 1)
problem_description: Statement
  
  Tak has N cards. On the i-th (1 \leq i \leq N) card is written an integer x_i.
  He is selecting one or more cards from these N cards, so that the average of
  the integers written on the selected cards is exactly A. In how many ways can
  he make his selection?
samples: [{"input": "4 8\n    7 9 8 9", "output": "5\n    \n\n  * The following are the 5 ways to select cards such that the average is 8:\n    * Select the 3-rd card.\n    * Select the 1-st and 2-nd cards.\n    * Select the 1-st and 4-th cards.\n    * Select the 1-st, 2-nd and 3-rd cards.\n    * Select the 1-st, 3-rd and 4-th cards.\n\n* * *"}, {"input": "3 8\n    6 6 9", "output": "0\n    \n\n* * *"}, {"input": "8 5\n    3 6 2 8 7 6 5 9", "output": "19\n    \n\n* * *"}, {"input": "33 3\n    3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3", "output": "8589934591\n    \n\n  * The answer may not fit into a 32-bit integer."}]