startup

term.clear()
term.setCursorPos(1, 1)

while true do
  term.clear()
  term.setCursorPos(1, 1)

  print("Enter a floor number. Underground levels are negative.")

  input = read()

  if input == "-2" then
    rs.setAnalogOutput("back", 1)
    rs.setAnalogOutput("back", 2)
  elseif input == "-1" then

  elseif input == "0" then

  else
    print("Invalid input.")
    sleep(2)
  end

end