function _show(n){
    theN = document.getElementById(n);
    if (theN==null){
        return;
    }
    theN.style.display = 'list-item';
}
function _hide(n){
    theN = document.getElementById(n);
    if (theN==null){
        return;
    }
    theN.style.display = 'none';
}