function calculate_total()
 {

   var tickets = document.forms['calc']['tickets'].value;
   var p1 = 0;
   var p2 = 0;
   var p3 = 0;
   var p4 = 0;
   var p5 = 0;
   var pa1 = 0;
   var cost = 0;

   if (tickets.length == 0)
   {
      return;
   }

   if (tickets > 100)
{
	alert("Oops, you can't buy more than 100 tickets");
return;

}

if(tickets < 0)
{
alert("Oops, you can't buy negative number of tickets. tyr math.com");
return;

}




   cost = 2*tickets;	

   p1 = 5 * (tickets*(100-tickets)*(99-tickets)*(98-tickets)*(97-tickets))*(1/(100*99*98*97*96));
   p2 = 10 * (tickets*(tickets-1)*(100-tickets)*(99-tickets)*(98-tickets))*(1/(100*99*98*97*96));
   p3 = 10 * (tickets*(tickets-1)*(tickets-2)*(100-tickets)*(99-tickets))*(1/(100*99*98*97*96));
   p4 = 5 * (tickets*(tickets-1)*(tickets-2)*(tickets-3)*(100-tickets))*(1/(100*99*98*97*96));
   p5 = (tickets*(tickets-1)*(tickets-2)*(tickets-3)*(tickets-4))*(1/(100*99*98*97*96));
   
   pa1 = p1+p2+p3+p4+p5;
 
   p1 = p1 *100;
   p2 = p2 *100;
   p3 = p3 *100;
   p4 = p4 *100;
   p5 = p5 *100;
   pa1 = pa1 *100;	
  

   document.getElementById('cost').value=cost;
   document.getElementById('1packs').value=p1.toFixed(2);
   document.getElementById('2packs').value=p2.toFixed(2);
   document.getElementById('3packs').value=p3.toFixed(2);
   document.getElementById('4packs').value=p4.toFixed(2);
   document.getElementById('5packs').value=p5.toFixed(2);
   document.getElementById('atleast1packs').value=pa1.toFixed(5);	


 } // end function definition