function swap(n, m)
{
    //Replaces div 'n' with 'm'
    //hide all, turn off both divs
    document.getElementById('div-' + n.toString()).style.display = 'none';
    document.getElementById('div-' + m.toString()).style.display = 'none';

    //show indicated div
    document.getElementById('div-' + m.toString()).style.display='block';
}