How do i add a new position to this script when clicked?

How do i add a new position to this script when clicked the first time go to that position, when clicked again go to a different position.

  #pragma strict
  function Update ()
  {
  if (Input.GetMouseButton(0))
  {
  Camera.main.transform.position = Vector3(51,3,0);
  }
  }

Use the script below, set the positions in the inspector.

  var positions : Vector3[];
  var currentPosition = 0;

  function OnMouseDown()
  {
        Camera.main.transform.position = positions[currentPosition++];
        if(currentPosition >= positions.Length) currentPosition = 0;
   
  }