function delkadivu() {
  var delka1 = document.getElementById('leftmenu').clientHeight;
  var delka2 = document.getElementById('obsah').clientHeight;
  if (delka1 < delka2) { document.getElementById('leftmenu').style.height = delka2+"px";
  } else { if (delka1 > delka2 && delka2 > 530) { document.getElementById('leftmenu').style.height = delka2+"px";       
         } else { document.getElementById('leftmenu').style.height = "530px"; 
         }       
  }
}