$(function () {
  setInterval(function(){ChangeSlide();}, 4000);
                         
  function ChangeSlide()
  {
    var currentElem = $("#slides > div.shown");
    var nextElem;
    
    if (currentElem.next().length == 0)
    {
      nextElem = $("#slides > div").eq(0);
    }
    else
    {
      nextElem = currentElem.next();
    }
    currentElem.removeClass("shown").addClass("hidden");
    nextElem.removeClass("hidden").addClass("shown");
  }
    });