$(document).ready(
    function()
    {
        var countLi = 0;
        var countBlock = 0;
        
        $("div#advantages li a").each(
            function()
            {
                if(countLi == 0)
                {
                    $(this).parent("li").addClass("active");
                }
                
                countLi++;
            }
        );
        
        $("div#change-container div.change-page").each(
            function()
            {
                if(countBlock == 0)
                {
                    $(this).addClass("active");
                }
                
                countBlock++;
            }
        );
        
        
        $("div#advantages li a").click(
            function()
            {
                if($(this).parent("li").attr("class") != "active")
                {
                    $("div#advantages li.active").removeClass("active");
                    $(this).parent("li").addClass("active");
                    
                    $("div#change-container div.active").removeClass("active");
                    
                    $("div#change-container div#block-"+$(this).attr("id")).addClass("active");
                }
            }
        );
    }
);