function addLoadEvent(func) {
  var oldonload = window.onload;
  if (typeof window.onload != 'function') {
    window.onload = func;
  } else {
    window.onload = function() {
      oldonload();
      func();
    }
  }
}
var slideshow = {
	config:{
				theImage : 'virtual',
				prev : 'prev',
				next : 'next',
				count : 1,
				min : 1,
				max : 80
	          },
	init:function(){
			var nextLink = document.getElementById(slideshow.config.next);
			var prevLink = document.getElementById(slideshow.config.prev);
			var mainPic = document.getElementById(slideshow.config.theImage);
			nextLink.onclick = function(){
				if (slideshow.config.count == slideshow.config.max){
					slideshow.config.count = slideshow.config.min;
				} else {
					slideshow.config.count+= 1;
				}
				mainPic.setAttribute("src","images/exterior" + slideshow.config.count + ".jpg");
			}
			prevLink.onclick = function(){
				if (slideshow.config.count == slideshow.config.min) {
					slideshow.config.count = slideshow.config.max;
				} else {
					slideshow.config.count-= 1;
				}
				mainPic.setAttribute("src","images/exterior" + slideshow.config.count + ".jpg");
			}
						
		  }
}
addLoadEvent(slideshow.init);