how to detect if the mouse has clicked off an object unity code example

Example: how to detect a mouse click in unity

using UnityEngine;
using System.Collections;

		if (Input.GetMouseButtonDown(0)) {
        	//Left Mouse Button
        } else if (Input.GetMouseButtonDown(1)) {
        	//Right Mouse Button
        } if (Input.GetMouseButtonDown(2)) {
        	//Middle Mouse Button
        }