function hidesubmenus(pocet,zobraz) {
for(i = 1; i <= pocet; i++) {
document.getElementById('menu'+i).style.backgroundImage = 'none';
document.getElementById('submenu'+i).style.display = 'none';
}
document.getElementById('menu'+zobraz).style.backgroundImage = 'url(/images/submenu-arrow.jpg)';
document.getElementById('submenu'+zobraz).style.display = 'block';
}

function showsubmenus(pocet,zobraz) {
for(i = 1; i <= pocet; i++) {
document.getElementById('menu'+i).style.backgroundImage = 'none';
document.getElementById('submenu'+i).style.display = 'none';
}
document.getElementById('menu'+zobraz).style.backgroundImage = 'url(/images/submenu-arrow.jpg)';
document.getElementById('submenu'+zobraz).style.display = 'block';
}