function house_num(){
	var results=0;
	var num = document.getElementById('num').value;
	for(i=0;i<num;i++){
	    var house_num=document.getElementById("house_num["+i+"]").value;
		results+=house_num;
	}
	if(results==0){
	    alert('您需要预定的房间数不能为零!');
	}
}