$( "#slider-range" ).slider({
        range: "range",
        min: 0,
        max: 500,
        values: [ 450, 500 ],
        slide: function( event, ui ) {
            $( "#amount" ).val( ui.values[ 0 ] + "zł - " + ui.values[ 1 ] + "zł" );
        }
    });
    $( "#amount" ).val( $( "#slider-range" ).slider( "values", 0 ) + "zł" +
            " - " + $( "#slider-range" ).slider( "values", 1 ) + "zł" );