stair

function failsafe()
  while not turtle.forward() do
     turtle.dig()
  end
end

--function failsafeDown()
  --while not turtle.Down() do
    --turtle.digDown()
  --end
--end

function mineLeft()
  turtle.turnLeft()
  while turtle.detect() do
    turtle.dig()
  end
  turtle.turnRight()
end

function DDLeft()
  turtle.digDown()
  turtle.down()
  mineLeft()
  turtle.up()
  turtle.dig()
  mineLeft()
  failsafe()
  mineLeft()
  turtle.dig()
  turtle.digDown()
  failsafe()
  mineLeft()
  turtle.back()
  turtle.down()
  mineLeft()
end

DDLeft()