title: Autofill the missing variable (input)
body: <p>Hi most supportive community in the world.
  There is there input in my app. if you put only two of them you can easily calculate the other one. So i want to make it if you only put two of them, number there whichever this is, being calculated and the result being put in input place and be visible to user in real-time.completely automatic without needing to press any button from user. how do i do it? I'm using JavaScript.
  Regards and thanks to everyone reading this.</p>