function slide(){
  var one = document.getElementById('div1').style.top;
  var two = document.getElementById('div2').style.top;
  var three = document.getElementById('div3').style.top;
  var four = document.getElementById('div4').style.top;
  var five = document.getElementById('div5').style.top;
  var six = document.getElementById('div6').style.top;
  
  document.getElementById('div1').style.top = (parseInt(one) + 5 + "px");
  document.getElementById('div2').style.top = (parseInt(two) + 5 + "px");
  document.getElementById('div3').style.top = (parseInt(three) + 5 + "px");
  document.getElementById('div4').style.top = (parseInt(four) + 5 + "px");
  document.getElementById('div5').style.top = (parseInt(five) + 5 + "px");
  document.getElementById('div6').style.top = (parseInt(six) + 5 + "px");
  
  
  if(parseInt(one) > 2500){
      document.getElementById('div1').style.top = -500 + "px";
  }
  if(parseInt(two) > 2500){
      document.getElementById('div2').style.top = -500 + "px";
  }
  if(parseInt(three) > 2500){
      document.getElementById('div3').style.top = -500 + "px";
  }
  if(parseInt(four) > 2500){
      document.getElementById('div4').style.top = -500 + "px";
  }
  if(parseInt(five) > 2500){
      document.getElementById('div5').style.top = -500 + "px";
  }
  if(parseInt(six) > 2500){
      document.getElementById('div6').style.top = -500 + "px";
  }
  
  if(parseInt(one) == 0 || parseInt(two) == 0 || parseInt(three) == 0 || parseInt(four) == 0 || parseInt(five) == 0 || parseInt(six) == 0){
    setTimeout('slide()', 3500);
  }else{
    setTimeout('slide()', 80);
  }
}