;(function( $ ){
    $.fn.parallax = function( position ){
        var pos = $('#layer1').css('background-position');
        var jea = pos.split('px');

        var summa = parseInt(jea[0]);
        var newValue1 = summa + 'px ' + jea[1] + 'px';
        var summa = parseInt(jea[0])*2;
        var newValue2 = summa + 'px ' + jea[1] + 'px';
        var summa = parseInt(jea[0])*3;
        var newValue3 = summa + 'px ' + jea[1] + 'px';
        var summa = parseInt(jea[0])*4;
        var newValue4 = summa + 'px ' + jea[1] + 'px';
        var summa = parseInt(jea[0])*4;
        var newValue5 = summa + 'px ' + jea[1] + 'px';
        $('#layer1').css('background-position', newValue1);
        $('#layer2').css('background-position', newValue2);
        $('#layer3').css('background-position', newValue3);
        $('#layer4').css('background-position', newValue4);
        $('#layer5').css('background-position', newValue5);
    }
})( jQuery );