for (ia=0; ia<wood; ia++){
document.write('<IMG ID="'+ia+'" src="wood.gif" alt="pylon" STYLE="position:absolute; top:-1000px; left:280px; width:40px; height:100px">')
}
for (ia=wood; ia<wood+pylon; ia++){
document.write('<IMG ID="'+ia+'" src="pylon.gif" alt="pylon" STYLE="position:absolute; top:-1000px; left:280px; width:40px; height:100px">')
}