Make an object go to a location with only one touch

Hi all,

I'd like to make a ball go to a specific point with only one touch. Each time the screen is pressed the ball moves to a different location. I only want it to move once and then reset. Thank you. My code is below.

 // Use this for initialization
 void Start()
 {
     Vector3 position = new Vector3(transform.position.x, transform.position.y, transform.position.z);
 }

 Vector3 myposition;

 //make on touch
 void Update ()
 {
     if (Input.touchCount > 0) {
         Touch touch = Input.GetTouch (0);
          //(touch.phase == TouchPhase.Began) 
             Vector3 touchPosition = Camera.main.ScreenToWorldPoint (new Vector3 (touch.position.x, touch.position.y, 25));
             myposition = touchPosition;
             transform.position = Vector3.Lerp (transform.position, myposition, Time.deltaTime*10);

     }
 }

}