input: Write a function to optimize a route from startX to endX.
  assert optimize_route(0, 5) == [0, 1, 2, 3, 4, 5]
  assert optimize_route(2, 8) == [2, 3, 4, 5, 6, 7, 8]
  assert optimize_route(5, 9) == [5, 6, 7, 8, 9]
output: def optimize_route(startX, endX):
      return list(range(startX, endX + 1))