function change(num,sum,location){
	//num为此件标识，sum为总数
	for(j=1;j<=sum;j++){
		var items = document.getElementById(location+'button'+j);
		var layers = document.getElementById(location+j);
		if(j==num){
			items.className = 'on';
			layers.style.display = 'block';
		}
		else{
			items.className = 'button';
			layers.style.display = 'none';
		}
	}
}