var Num=2;
var NumR=Num+1;
var NumL=Num-1;

function preloadImg() { 
	var args = preloadImg.arguments;
	document.imageArray = new Array(args.length);
	for(var i=0; i<args.length; i++) {
		document.imageArray[i] = new Image;
		document.imageArray[i].src = args[i];
	}
}

function scrollImg(Dir) {
	var Picts=document.imageArray.length/2;

	if (Dir=='next') {
		Num==Picts ? Num=1 : Num++;
		NumR==Picts ? NumR=1 : NumR++;
		NumL==Picts ? NumL=1 : NumL++;
	}
	
	if (Dir=='prev') {
		Num==1 ? Num=Picts : Num--;	
		NumR==1 ? NumR=Picts : NumR--;	
		NumL==1 ? NumL=Picts : NumL--;	
	}
	
	document.getElementById('photo').style.backgroundImage='url(images/photo'+Num+'.jpg)';
	document.getElementById('thumb1').src='images/thumb'+(NumL)+'.jpg';
	document.getElementById('thumb2').src='images/thumb'+(NumR)+'.jpg';
}