var nextPage, prevPage;

function getLocation() {
 var thispage = window.location;
 myReg = /index(.*)\.html/i;
 match = myReg.exec(thispage);
 nPage=match[1];
 nextPage = parseInt(nPage)+1;
 prevPage = parseInt(nPage)-1;
}

getLocation();

function goNext(){
	window.location="index"+nextPage+".html";
}

function goPrev(){
	window.location="index"+prevPage+".html";
}