How to only get touch on specific object?

First I was trying to make 2 "buttons" work like right input and left input with GetMouseButtonDown, but since it doesn't support Multi Touch, decided to change to Touch Inputs.

I'm using this code (in the left button):

 using UnityEngine;
 using System.Collections;
 
 public class TouchLeft : MonoBehaviour {
     public GameObject projectile;
     void Update() {
         int i = 0;
         while (i < Input.touchCount) {
             if (Input.GetTouch(i).phase == TouchPhase.Began)
             GameObject.Find ("GavielG_Charge").GetComponent<Platformer2DUserControl> ().h = -1;
             else
                 GameObject.Find ("GavielG_Charge").GetComponent<Platformer2DUserControl> ().h = 0;
         
             ++i;
         }
     }
 } 

But using it makes all the screen touchable, anyone can help me make the script only set the button touchable?