function showcrossed() {
    numitems = document.getElementById('numitems').value;
    for (i=1; i<=numitems; i++){
        if (document.getElementById('item'+i).className == 'tobecrossed'){
            document.getElementById('item'+i).className = 'crossed';
        }
    }
}
function hidecrossed() {
    numitems = document.getElementById('numitems').value;
    for (i=1; i<=numitems; i++){
        if (document.getElementById('item'+i).className == 'crossed'){
            document.getElementById('item'+i).className = 'tobecrossed';
        }
    }
}