// JavaScript Document
 function change(e){
	 var buttom = document.getElementById("buttom");
	 var button = buttom.childNodes;
	 button[e].style.color= '#000';
	 
	 }
 function goback(e){
	 var buttom = document.getElementById("buttom");
	 var button = buttom.childNodes;
	 button[e].style.color = '#666666';
	 
	 }