drill

d=20

function oneDown()
  turtle.select(1)
  while not turtle.forward() do
    turtle.dig()
  end
  turtle.digUp()
  turtle.digDown()
  turtle.down()
  turtle.placeDown()
end

function placeTorch()
  turtle.select(2)
  turtle.placeUp()
end


while d > 0 do

  for i=1,2 do
    oneDown()
    d = d - 1
  end

  placeTorch()
  turtle.turnLeft()

end