function citys_ajax(city_field, reg_field, city_box, ans) {
						    	document.getElementById(city_box).disabled = true;
						    	
						        JsHttpRequest.query(
						            'citys_ajax.php', // backend
						            {
						                'str': document.getElementById(reg_field).value,
						                'field': city_field,
						                'city_box': city_box
						            },
						           
						            function(result, errors) {
						                if (result) {
						                    document.getElementById(ans).innerHTML = 
						                        result;
						                }
						            },
						            false  // do not disable caching
						        );
						    }