function selectLayer1(i)
{
 switch(i)
 { 
  case 21:
document.getElementById("bbs_s21").style.display="block";
document.getElementById("bbs_s22").style.display="none";
document.getElementById("bbs_s23").style.display="none";
document.getElementById("bbs_s24").style.display="none";
document.getElementById("bbs_s25").style.display="none";
document.getElementById("bbs_s26").style.display="none";
document.getElementById("bbs_s27").style.display="none";
document.getElementById("bbs_s28").style.display="none";
document.getElementById("bbs_s29").style.display="none";
 break;
case 22:
document.getElementById("bbs_s21").style.display="none";
document.getElementById("bbs_s22").style.display="block";
document.getElementById("bbs_s23").style.display="none";
document.getElementById("bbs_s24").style.display="none";
document.getElementById("bbs_s25").style.display="none";
document.getElementById("bbs_s26").style.display="none";
document.getElementById("bbs_s27").style.display="none";
document.getElementById("bbs_s28").style.display="none";
document.getElementById("bbs_s29").style.display="none";
 break;
 case 23:
document.getElementById("bbs_s21").style.display="none";
document.getElementById("bbs_s22").style.display="none";
document.getElementById("bbs_s23").style.display="block";
document.getElementById("bbs_s24").style.display="none";
document.getElementById("bbs_s25").style.display="none";
document.getElementById("bbs_s26").style.display="none";
document.getElementById("bbs_s27").style.display="none";
document.getElementById("bbs_s28").style.display="none";
document.getElementById("bbs_s29").style.display="none";
 break;
 case 24:
document.getElementById("bbs_s21").style.display="none";
document.getElementById("bbs_s22").style.display="none";
document.getElementById("bbs_s23").style.display="none";
document.getElementById("bbs_s24").style.display="block";
document.getElementById("bbs_s25").style.display="none";
document.getElementById("bbs_s26").style.display="none";
document.getElementById("bbs_s27").style.display="none";
document.getElementById("bbs_s28").style.display="none";
document.getElementById("bbs_s29").style.display="none";
 break;
case 25:
document.getElementById("bbs_s21").style.display="none";
document.getElementById("bbs_s22").style.display="none";
document.getElementById("bbs_s23").style.display="none";
document.getElementById("bbs_s24").style.display="none";
document.getElementById("bbs_s25").style.display="block";
document.getElementById("bbs_s26").style.display="none";
document.getElementById("bbs_s27").style.display="none";
document.getElementById("bbs_s28").style.display="none";
document.getElementById("bbs_s29").style.display="none";
 break;
 case 26:
document.getElementById("bbs_s21").style.display="none";
document.getElementById("bbs_s22").style.display="none";
document.getElementById("bbs_s23").style.display="none";
document.getElementById("bbs_s24").style.display="none";
document.getElementById("bbs_s25").style.display="none";
document.getElementById("bbs_s26").style.display="block";
document.getElementById("bbs_s27").style.display="none";
document.getElementById("bbs_s28").style.display="none";
document.getElementById("bbs_s29").style.display="none";
 break;
 case 27:
document.getElementById("bbs_s21").style.display="none";
document.getElementById("bbs_s22").style.display="none";
document.getElementById("bbs_s23").style.display="none";
document.getElementById("bbs_s24").style.display="none";
document.getElementById("bbs_s25").style.display="none";
document.getElementById("bbs_s26").style.display="none";
document.getElementById("bbs_s27").style.display="block";
document.getElementById("bbs_s28").style.display="none";
document.getElementById("bbs_s29").style.display="none";
 break;
 case 28:
document.getElementById("bbs_s21").style.display="none";
document.getElementById("bbs_s22").style.display="none";
document.getElementById("bbs_s23").style.display="none";
document.getElementById("bbs_s24").style.display="none";
document.getElementById("bbs_s25").style.display="none";
document.getElementById("bbs_s26").style.display="none";
document.getElementById("bbs_s27").style.display="none";
document.getElementById("bbs_s28").style.display="block";
document.getElementById("bbs_s29").style.display="none";
 break;
 case 29:
document.getElementById("bbs_s21").style.display="none";
document.getElementById("bbs_s22").style.display="none";
document.getElementById("bbs_s23").style.display="none";
document.getElementById("bbs_s24").style.display="none";
document.getElementById("bbs_s25").style.display="none";
document.getElementById("bbs_s26").style.display="none";
document.getElementById("bbs_s27").style.display="none";
document.getElementById("bbs_s28").style.display="none";
document.getElementById("bbs_s29").style.display="block";
 break;

 }
}