fence

blocks = 0
fuel = turtle.getFuelLevel()
fences = turtle.getItemCount(1)

function refuel()
  turtle.select(15)
  turtle.place()
  turtle.select(14)
  turtle.suck()
  turtle.refuel()
  turtle.select(15)
  turtle.dig()
end

function refill()
  turtle.select(16)
  turtle.place()
  turtle.select(1)
  turtle.suck()
  turtle.select(16)
  turtle.dig()
end

function chunks()
  blocks = 0
  turtle.turnLeft()
  turtle.dig()
  turtle.select(12)
  turtle.place()
  turtle.turnLeft()
  for i = 1, 16 do
    turtle.forward()
  end
  turtle.turnRight()
  turtle.dig()
  turtle.turnRight()
  for i = 1, 16 do
    turtle.forward()
  end
end

function place()
  fuel = turtle.getFuelLevel()
  fences = turtle.getItemCount(1)
  if fuel<1000 then
    refuel()
  end
  if fences<1 then
    refill()
  end
  turtle.select(1)
  turtle.dig()
  turtle.digDown()
  turtle.placeDown()
  turtle.forward()
  blocks = blocks + 1
  if blocks==16 then
    chunks()
  end
end

for i=1,4 do
  for i=1,63 do
    place()
  end
  turtle.turnRight()
end