input: Write a function to extract the first name and the last name from a given full name.
  assert extract_names('John Smith') == ('John', 'Smith')
  assert extract_names('Jane Doe') == ('Jane', 'Doe')
  assert extract_names('Alice Johnson') == ('Alice', 'Johnson')
output: def extract_names(full_name):
      parts = full_name.split()
      first_name = parts[1]
      last_name = parts[-1]
      return first_name, last_name