function setFocus(i)
{
selectLayer(i);
}
function selectLayer(i)
{
switch(i)
{
case 1:
document.getElementById("N1").style.display="block";
document.getElementById("N2").style.display="none";
document.getElementById("N3").style.display="none";
break;
case 2:
document.getElementById("N1").style.display="none";
document.getElementById("N2").style.display="block";
document.getElementById("N3").style.display="none";
break;
case 3:
document.getElementById("N1").style.display="none";
document.getElementById("N2").style.display="none";
document.getElementById("N3").style.display="block";
break;

}
}