var imgNumber=1;//this is the array ordinal, start at 1 because arr[0] is displayed already on page load
var numImgs=36;
var conCat;
var images = new Array();
  
   images[0]="18.jpg";
   images[1]="xx";
   images[2]="19.jpg";
   images[3]="28.jpg";
   images[4]="xx";
   images[5]="xx";
   images[6]="1.jpg";
   images[7]="21.jpg";
   images[8]="xx";
   images[9]="xx";
   images[10]="20.jpg";
   images[11]="24.jpg";
   images[12]="30.jpg";
   images[13]="27.jpg";
   images[14]="35.jpg";
   images[15]="9.jpg";
   images[16]="12.jpg";
   images[17]="15.jpg";
   images[18]="2.jpg";
   images[19]="10.jpg";
   images[20]="13.jpg";
   images[21]="14.jpg";
   images[22]="36.jpg";
   images[23]="25.jpg";
   images[24]="22.jpg";
   images[25]="xx";
   images[26]="29.jpg";
   images[27]="31.jpg";
   images[28]="32.jpg";
   images[29]="39.jpg";
   images[30]="38.jpg";
   images[31]="26.jpg";
   images[32]="37.jpg";
   images[33]="3.jpg";
   images[34]="8.jpg";
   images[35]="xx";
   images[36]="16.jpg";
   images[37]="17.jpg";
   images[38]="5.jpg";
   images[39]="34.jpg";
   images[40]="6.jpg";
   images[41]="11.jpg";
 
   
function changePic()
{
               
     if (imgNumber <= images.length-1)
       {
         if(images[imgNumber]=="xx")
         {
                    alert ("XX found")
                    imgNumber++;
                    changePic();
                    alert ("yy")
         }
        document.mainPic.src=images[imgNumber];

           
       }
      
    imgNumber++;

}