function show(a) {
    document.getElementById(a).style.visibility='visible';
    }

function hide(a) {
    document.getElementById(a).style.visibility='hidden';
    }

function openmenu(a) {
    if(document.getElementById(a).style.display=='block') document.getElementById(a).style.display='none';
    else document.getElementById(a).style.display='block';
    }