How to alternate character with one touch?

So I want a script in which if the player touches the screen one time, the character goes up. If he/she touches the screen again, it goes down. This alternates per tap on the screen.

Sorry in advance if this is a stupid question. I’m new to the programming world.

void Update(){

	if (Input.GetMouseButtonDown (0)) {



                        //add upForce


             //add down force