input: Write a function to find the missing number in a list of integers using set operations.
  assert missing_number([7, 5, 6, 4, 2]) == 1
  assert missing_number([1, 2, 3, 5]) == 4
  assert missing_number([10, 7, 8, 9, 2, 4, 1, 6, 3]) == 5
output: def missing_number(nums):
      n = len(nums) + 1
      full_set = set(range(1, n + 1))
      nums_set = set(nums)
      missing = full_set - nums_set
      return missing.pop()