input: Write a function to find the maximum length of a subset such that for any two elements, the difference between them is consistent with the adjacent pairs in the original array.
  assert findMaxSubset([1, 2, 4, 7, 8, 11, 14, 15]) == 5
  assert findMaxSubset([1, 3, 5, 7, 9, 11, 13]) == 7
  assert findMaxSubset([1, 3, 6, 10, 15, 21]) == 2
output: def findMaxSubset(arr):
      if not arr:
          return 0
  
      max_len = 1
      diff_dict = {}
  
      for i in range(len(arr)):
          for j in range(i + 1, len(arr)):
              diff = arr[j] - arr[i]
              if (i, diff) in diff_dict:
                  diff_dict[(j, diff)] = diff_dict[(i, diff)] + 1
              else:
                  diff_dict[(j, diff)] = 2
  
              max_len = max(max_len, diff_dict[(j, diff)])
  
      return max_len