var URL="";

function getsheetval(sheet)
{
if (gup("sheet"))
   {sheet=gup("sheet");}
if (sheet == null) {sheet=0};
return (sheet);
}




function sheetbounds(sheet)
{
var totalsheets=35;
if (sheet > totalsheets) {sheet=0}
if (sheet < 0) {sheet=totalsheets}
return (sheet);
}


function nextsheet()
{
var sheet = getsheetval(sheet);
sheet++;
sheet=sheetbounds(sheet);
gotosheet(sheet);
}

function prevsheet()
{
var sheet = getsheetval(sheet);
sheet--;
sheet=sheetbounds(sheet);
gotosheet(sheet);
}

function gotosheet(sheet)
{
window.location=URL+"?sheet="+sheet;
}


function displaysheet()
{
 var sheet = getsheetval(sheet);
 eval("document.sheet.src='"+sheet+".jpg'");
}


function gup( name )
{
name = name.replace(/[\[]/,"\\\[").replace(/[\]]/,"\\\]");
var regexS = "[\\?&]"+name+"=([^&#]*)";
var regex = new RegExp( regexS );
var results = regex.exec( window.location.href );
if( results == null )
return "";
else
return results[1];
}