function change2(i)
{
    var j;
	for (j=1;j<4;j++)
	{
		if(j==i)
		{
		    //??????
		 if(document.getElementById("a"+j).style.display=="none"){
			document.getElementById("a"+j).style.display="";
			document.getElementById("b"+j).className="njian";}
			else{document.getElementById("a"+j).style.display="none";
			     document.getElementById("b"+j).className="njia";
			}		   
		}
	}
}