input: Write a function to find the index of a given number in a sorted list.
  assert index_of(5, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]) == 4
  assert index_of(10, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]) == 9
  assert index_of(3, [1, 2, 3, 4, 5]) == 2
  assert index_of(11, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]) == -1
output: def index_of(number, sorted_list):
      try:
          return sorted_list.index(number)
      except ValueError:
          return -1