Remove Quit Functionality from Mac/PC Build

Basically I have developed fullscreen pc/mac game. I want to remove default quit game functionality from my game.

Cmd + Q → Mac
Alt + F4 → PC

These are two way for quiting for game forcefully. I want to stop this.
Pleaes give me some suggestion for this.

EDIT:

void Update ()
	{

//		if (Input.GetKeyDown (KeyCode.Q) && Input.GetKeyDown (KeyCode.LeftCommand)) {
//			isIgnoreQuit = true;
////			Application.CancelQuit ();
//		}

		// app quit functionality
		if (!isQuit && Input.GetKey (KeyCode.Q) && Input.GetKey (KeyCode.E) && Input.GetKey (KeyCode.T) && Input.GetKey (KeyCode.U) && ((Input.GetKey (KeyCode.Keypad0) && Input.GetKey (KeyCode.Keypad9))
		    || (Input.GetKey (KeyCode.Alpha0) && Input.GetKey (KeyCode.Alpha9)))) {
			isQuit = true;
			Application.Quit ();
		}
	}

//	void OnApplicationQuit ()
//	{
//		if (isIgnoreQuit)
//			Application.CancelQuit ();
//
//		isIgnoreQuit = false;
//	}

In above code, keypress event don’t have any effect.

Untested, but I imagine

void OnApplicationQuit() {
  Application.CancelQuit();
}

might do it.