function pokoje(from_id,to_id)
{
  var from = document.getElementById(from_id);
  var to = document.getElementById(to_id);
  var option;
  while (to.options.length > 0)
    to.options[0]=null;
  var k=0;
  for (i=Math.ceil(from.options[from.selectedIndex].value/2);i<=from.options[from.selectedIndex].value;i++)
  {
    option = new Option(i,i);
    to.options[k]= option;
    k++;
  }
  to.selectedIndex=0;
};