function GID(name) {
    return document.getElementById(name);
}

function openmenu(numb) {
   var i = 1;
   var elm = GID('N' + i);

   while ((elm = GID('N' + i)) == null) i++;

   while (elm != null) {
       if (i == numb) elm.style.display = 'block';
       else elm.style.display = 'none';
       i++;
       elm = GID('N' + i);
   }
}

function closemenu(numb) {
   var elm = GID('N' + numb);
   elm.style.display = 'none';
}

function menumark(th) {
    th.style.backgroundColor = '#E0E0E0';
}

function menuunmark(th) {
    th.style.backgroundColor = '#FFFFFF';
}