output_description: Print the maximum value of D that enables you to visit all the cities.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N X
      x_1 x_2 ... x_N
attempt: n, x = map(int, input().split())
  a = list(map(int, input().split()))
  res, ans = [], 0
  for i in range(n):
      res.append(abs(a[i] - x))
  # print(min(res))
  res.sort()
  ans = res[0]
  cnt = 0
  if n > 1:
      num = min((n - 1), 11)
      for j in range(2, num):
          cmp = a[0] % res[0] * j
          for s in range(n):
              if a[s] % res[0] * j != cmp:
                  break
              else:
                  cnt += 1
          if cnt == n:
              ans = res[0] * j
  print(ans)
  
problem_description: Statement
  
  There are N cities on a number line. The i-th city is located at coordinate
  x_i.
  
  Your objective is to visit all these cities at least once.
  
  In order to do so, you will first set a positive integer D.
  
  Then, you will depart from coordinate X and perform Move 1 and Move 2 below,
  as many times as you like:
  
    * Move 1: travel from coordinate y to coordinate y + D.
    * Move 2: travel from coordinate y to coordinate y - D.
  
  Find the maximum value of D that enables you to visit all the cities.
  
  Here, to visit a city is to travel to the coordinate where that city is
  located.
samples: [{"input": "3 3\n    1 7 11", "output": "2\n    \n\nSetting D = 2 enables you to visit all the cities as follows, and this is the\nmaximum value of such D.\n\n  * Perform Move 2 to travel to coordinate 1.\n  * Perform Move 1 to travel to coordinate 3.\n  * Perform Move 1 to travel to coordinate 5.\n  * Perform Move 1 to travel to coordinate 7.\n  * Perform Move 1 to travel to coordinate 9.\n  * Perform Move 1 to travel to coordinate 11.\n\n* * *"}, {"input": "3 81\n    33 105 57", "output": "24\n    \n\n* * *"}, {"input": "1 1\n    1000000000", "output": "999999999"}]