input: Write a python function to find the missing number from a list of numbers.
  assert find_missing_number([2, 3, 1, 5]) == 4
  assert find_missing_number([1, 2, 4, 5, 6]) == 3
  assert find_missing_number([10, 9, 8, 7, 6, 5, 4, 3, 2]) == 1
output: def find_missing_number(numbers):
      n = len(numbers) + 1
      total_sum = n * (n + 1) // 2
      actual_sum = sum(numbers)
      return total_sum - actual_sum