input: Write a python function to compare two numbers and return 0 if they are equal, 1 if the first number is greater, and -1 if the second number is greater.
  assert compare_numbers(5, 10) == -1
  assert compare_numbers(10, 5) == 1
  assert compare_numbers(7, 7) == 0
output: def compare_numbers(a, b):
      if a == b:
          return 0
      elif a > b:
          return 1
      else:
          return -1