function getfirst() {
	var gif1=document.getElementById("lgif");
	var gif2=document.getElementById("rgif");
	gif1.setAttribute("src","images/page01.gif");
	gif2.setAttribute("src","images/page02.gif");
	var pdf1=document.getElementById("lpdf");
	var pdf2=document.getElementById("rpdf");
	pdf1.setAttribute("href","images/pdfhi/page01.pdf");
	pdf2.setAttribute("href","images/pdfhi/page02.pdf");
}
function goback() {
    var gif1=document.getElementById("lgif");
	var gif2=document.getElementById("rgif");      
 	var pdf1=document.getElementById("lpdf");
	var pdf2=document.getElementById("rpdf");
    var temp=gif1.getAttribute("src");
    var strlen=temp.length;
    var strpos=temp.substr(strlen-6, 2);
    var minus1=strpos-1;
    var minus2=strpos-2;
      	if   (strpos == "01") {
            alert ("you are already at the beginning!")
         }
      	else if(strpos>12 & strpos<44) {
				gif1.setAttribute("src","images/page" + minus2 + ".gif");
				gif2.setAttribute("src","images/page" + minus1 + ".gif");
				pdf1.setAttribute("href","images/pdfhi/page" + minus2 + ".pdf");
				pdf2.setAttribute("href","images/pdfhi/page" + minus1 + ".pdf");
		 }
     	 else if(strpos==11) {
	     	 minus2="0"+minus2;
				gif1.setAttribute("src","images/page" + minus2 + ".gif");
				gif2.setAttribute("src","images/page" + minus1 + ".gif");
				pdf1.setAttribute("href","images/pdfhi/page" + minus2 + ".pdf");
				pdf2.setAttribute("href","images/pdfhi/page" + minus1 + ".pdf");
		 }	 
      	else if(strpos<=10) {
	      	minus1="0"+minus1;
	      	minus2="0"+minus2;
				gif1.setAttribute("src","images/page" + minus2 + ".gif");
				gif2.setAttribute("src","images/page" + minus1 + ".gif");
				pdf1.setAttribute("href","images/pdfhi/page" + minus2 + ".pdf");
				pdf2.setAttribute("href","images/pdfhi/page" + minus1 + ".pdf");
     	 }
}
function goforward() {
    var gif1=document.getElementById("lgif");
	var gif2=document.getElementById("rgif");      
 	var pdf1=document.getElementById("lpdf");
	var pdf2=document.getElementById("rpdf");
    var temp=gif1.getAttribute("src");
    var strlen=temp.length;
    var strpos=temp.substr(strlen-6, 2);
    var plus2=strpos-(-2);
    var plus3=strpos-(-3);
       	if   (strpos == "48") {
            alert ("you are already at the end!")
         }
      	else if(strpos>0 & strpos<=6){
	      	plus2="0"+plus2;
	      	plus3="0"+plus3;
				gif1.setAttribute("src","images/page" + plus2 + ".gif");
				gif2.setAttribute("src","images/page" + plus3 + ".gif");
				pdf1.setAttribute("href","images/pdfhi/page" + plus2 + ".pdf");
				pdf2.setAttribute("href","images/pdfhi/page" + plus3 + ".pdf");
     	 }
     	 else if(strpos==7) {
	     	 plus2="0"+plus2;
				gif1.setAttribute("src","images/page" + plus2 + ".gif");
				gif2.setAttribute("src","images/page" + plus3 + ".gif");
				pdf1.setAttribute("href","images/pdfhi/page" + plus2 + ".pdf");
				pdf2.setAttribute("href","images/pdfhi/page" + plus3 + ".pdf");
 	    }	 
      	else if(strpos>=9) {
				gif1.setAttribute("src","images/page" + plus2 + ".gif");
				gif2.setAttribute("src","images/page" + plus3 + ".gif");
				pdf1.setAttribute("href","images/pdfhi/page" + plus2 + ".pdf");
				pdf2.setAttribute("href","images/pdfhi/page" + plus3 + ".pdf");

     	 }
}
function getlast() {
	var gif1=document.getElementById("lgif");
	var gif2=document.getElementById("rgif");
	gif1.setAttribute("src","images/page47.gif");
	gif2.setAttribute("src","images/page48.gif");
	var pdf1=document.getElementById("lpdf");
	var pdf2=document.getElementById("rpdf");
	pdf1.setAttribute("href","images/pdfhi/page47.pdf");
	pdf2.setAttribute("href","images/pdfhi/page48.pdf");
}