input: Write a function to swap the values of two variables. If both variables are integers, perform the swap and return the swapped values as a tuple. If either of the variables is not an integer, return a string "Invalid input".
  
  def swap_variables(x, y):
      if isinstance(x, int) and isinstance(y, int):
          return (y, x)
      else:
          return "Invalid input"
  
  # Test cases
  assert swap_variables(5, 10) == (10, 5)
  assert swap_variables("a", 10) == "Invalid input"
  assert swap_variables(5, "b") == "Invalid input"
  assert swap_variables(15, 20) == (20, 15)
  assert swap_variables(3, 3) == (3, 3)
output: def swap_variables(x, y):
      if isinstance(x, int) and isinstance(y, int):
          return (y, x)
      else:
          return "Invalid input"