input: Write a function to create a dictionary where the keys are numbers between 1 and 15 (both included) and the values are the squares of the keys. If the given range is invalid, return an empty dictionary.
  assert create_square_dict(1, 15)=={1: 1, 2: 4, 3: 9, 4: 16, 5: 25, 6: 36, 7: 49, 8: 64, 9: 81, 10: 100, 11: 121, 12: 144, 13: 169, 14: 196, 15: 225}
  assert create_square_dict(3, 7)=={3: 9, 4: 16, 5: 25, 6: 36, 7: 49}
  assert create_square_dict(0, 10)=={}
  assert create_square_dict(10, 20)=={10: 100, 11: 121, 12: 144, 13: 169, 14: 196, 15: 225, 16: 256, 17: 289, 18: 324, 19: 361, 20: 400}
  assert create_square_dict(-5, 5)=={}
output: def create_square_dict(start, end):
      if start < 1 or end < 1 or start > end:
          return {}
      return {i: i**2 for i in range(start, end + 1)}