write("Please enter depth/2")
depth=read()

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

function cycle()
  dig()
  turtle.digDown()
  turtle.down()
  if not turtle.detectDown() then
    turtle.placeDown() end
  turtle.up()
end

turtle.up()
counter=0
for i=0, depth do
  cycle()
  turtle.turnRight()
  cycle()
  if counter==3 then
    turtle.turnRight()
    turtle.select(9)
    turtle.place()
    turtle.select(1)
    turtle.turnLeft()
    counter=0
  end
  turtle.turnLeft()
  cycle()
  turtle.turnLeft()
  cycle()
  turtle.turnRight()
  counter=counter+1
end

turtle.turnRight()
turtle.turnRight()
for i=0, depth*2 do
  turtle.forward()
end