var now="";

function opn(element) {
 if (now!=""){
  document.getElementById(now).style.display="none";
  now="";
 }
document.getElementById(element).style.display="block";
now=element;
}

function cls() {
 if (now!=""){
  document.getElementById(now).style.display="none";
  now="";
 }
}