var controller : CharacterController;    
    var oldHeight;    
    var newHeight: float;    
    var newPos;   
    var bf : boolean = false;    

    function Start () {    
    controller = GetComponent(CharacterController);    
    oldHeight = controller.height;    
    }    

   function Update() {       
   newPos = new Vector3(transform.position.x, transform.position.y + 0.7f, transform.position.z);   
              if (Input.GetKey(KeyCode.LeftControl)) {   
                  controller.height = newHeight;   
                  bf = true;   
              } else {   
              if (Input.GetKeyUp (KeyCode.LeftControl) && !Physics.Raycast (transform.position, Vector2.up)) {   
                  controller.height = oldHeight;   
                  transform.position = newPos;   
                  bf = false;   
              } else {   
              if (bf == true && !Physics.Raycast (transform.position, Vector2.up)) {   
              controller.height = oldHeight;   
                  transform.position = newPos;   
                  bf = false;   
              }   
              }   
              }   
   }