How to remove gravity when click

So I have this script in which when I click the gravity turns -1 and it stays that way until I click again, but I want the gravity to go back to normal the moment my click ends. Just like flappy birds.

function Update ()
{
   if(Input.GetButtonDown("Fire1"))
{
    Physics.gravity *= -1;
}
	
}

There is also Input.GetButtonUp. You’re currently checking if the button was pressed; you can also check if it was released, and flip gravity back to normal.