counter

while true do
    evt, arg1 = os.pullEvent("redstone")
    if rs.getInput("back", true) then
  turtle.select(1)
  for i=1, 4 do
    turtle.select(i)
    if turtle.getSelectedSlot() == 1 then
      print((turtle.getItemCount()-1)*10)
    elseif turtle.getSelectedSlot() == 2 then
      print((turtle.getItemCount()-1)*8)
    end
  end
  turtle.select(1)
    end
end