var isStart=true;
var nn;
var tt;
function next_img(){
resetPlay();
nn++;
if(nn > 3) nn=1;
setFocus(nn);
}

function setFocus(i)
{

 nn = i;
 selectLayer1(i);

}
function pre_img(){
resetPlay();
nn--;
if(nn < 1) nn=3;
setFocus(nn);
}

function selectLayer1(i)
{

 switch(i)
 {
 case 1:
document.getElementById("bbs_s1").style.display="block";
document.getElementById("bbs_s2").style.display="none";
document.getElementById("bbs_s3").style.display="none";
 break;
case 2:
document.getElementById("bbs_s1").style.display="none";
document.getElementById("bbs_s2").style.display="block";
document.getElementById("bbs_s3").style.display="none";
 break;
 case 3:
document.getElementById("bbs_s1").style.display="none";
document.getElementById("bbs_s2").style.display="none";
document.getElementById("bbs_s3").style.display="block";
 break;
 }
}