function next()
{
  var item=document.getElementById('main-pict');
  current=(current+1)%picts.length;
  item.style.backgroundImage='url('+picts[current]+')';
}

function prev()
{
  var item=document.getElementById('main-pict');
  current--;
  if(current<0)
  {
    current=picts.length-1;
  }
  item.style.backgroundImage='url('+picts[current]+')';
}