function $(id){return document.getElementById(id);}
function change_tab(tab_id,content_id,total,now){
	for(var i=1;i<=total;i++){
		$(tab_id+i).style.display = "none";
		$(content_id+i).style.display = "none";
	}
	$(tab_id+now).style.display = "block";
	$(content_id+now).style.display = "block";
}