input: Write a python function to check if an array can be sorted in non-decreasing order by executing any number of right shift operations. If it can, return True; otherwise, return False. If the array is empty, return True.
  assert is_sortable_by_shifting([3, 4, 5, 1, 2])==True
  assert is_sortable_by_shifting([3, 5, 10, 1, 2])==True
  assert is_sortable_by_shifting([4, 3, 1, 2])==False
  assert is_sortable_by_shifting([3, 5, 4, 1, 2])==False
  assert is_sortable_by_shifting([])==True
output: def is_sortable_by_shifting(arr):
      if not arr: 
          return True
      n = len(arr)
      count = 0
      for i in range(n):
          if arr[i] > arr[(i + 1) % n]:
              count += 1
      return count <= 1