disable multi touch on specific screen area

I'm currently developing unity 2d platformer game for android. Then, i'm implement touch control with screen position detection.

as you see, i split the screen to 3 pieces : 1 for move to left, 2 for move to right, and 3 for jump. here the lines :

     void Start () 
         {
             anim = gameObject.GetComponent<Animator>();
             w = Screen.width;
             h = Screen.height;
         }
     
     void Update ()
         {
             if (Input.touchCount > 0) {
                 while (k < Input.touchCount) {    
                     if (Input.GetTouch (k).position.y > h / 3 && Input.GetTouch (k).position.x < w / 2 ) {                                                
                         // Move your character right
                         moveToRight();
                         }
                     if (Input.GetTouch (k).position.y > h / 3 && Input.GetTouch (k).position.x > w / 2 ) { 
                         // Move your character left
                         moveToLeft();    
                         }
                     if (Input.GetTouch (k).position.y < h / 3 && anim.GetBool ("Grounded")) {    
                         // jumping
                         jumpPlayer();
                         }
                 ++k;
             }
         }

The script jus fine, work normally. But for any reason i want to disable multi touch finger on area 3, i have seen unity docs for disable multi touch : Input.multiTouchEnabled = false; , then i asign that bool to Jumping touch control (area 3) :

 if (Input.GetTouch (k).position.y < h / 3 && anim.GetBool ("Grounded")) {    
                         // jumping
                  Input.multiTouchEnabled = false;
                         jumpPlayer();
                     }

for any reason too, i assign Input.multiTouchEnabled = true on touch area 1 and 2. But not that i want. Every i touch area 3, multi touch is disable, but when i touch area 1 or 2, on area 3 it's still enable to multi touch. I Know the problem, because i set Input.multiTouchEnabled = true on touching area 1 and 2. but, it's not possible to set false multi touch on touching area 1 and 2. And finally, i have conclusion to disable multiTouch on screen area 3 (not with touch, but permanently). question is : How to disable multi touch on specific screen area ?, in this case on area number 3. any answers would be very helpful. Thanks.