function selectSlot()
  for i=1,16,1 do
    if turtle.getItemCount(i) > 0 then
      turtle.select(i)
    end
  end
end

function requireSlot()
  while turtle.getItemCount() == 0 do
    selectSlot()
  end
end

function refuel()
  while turtle.getFuelLevel() < 100 do
    for i=1,16,1 do
      turtle.select(i)
      turtle.refuel()
    end
  end
end

for x=1,4,1 do
  for z=1,65,1 do
    repeat
      refuel()
      requireSlot()
      turtle.placeUp()
    until turtle.forward()
  end
  
  turtle.turnRight()
end
