vquarry

local function tryRefuel()
  while turtle.getFuelLevel() < 1 do
    for i = 1, 16 do
      turtle.select(i)
      turtle.refuel(1)
      if turtle.getFuelLevel() > 0 then
        break
      end
    end
    turtle.select(1)
  end
end

local function up()
  tryRefuel()
  while not turtle.up() do
    turtle.digUp()
  end
end

local function down()
  tryRefuel()
  while not turtle.down() do
    turtle.digDown()
  end
end

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

local function xforward(dist)
  for i = 1, dist do
    forward()
    turtle.digUp()
    turtle.digDown()
  end
end

local function rCorner()
  turtle.turnRight()
  turtle.dig()
  forward()
  turtle.digUp()
  turtle.digDown()
  turtle.turnRight()
end

local function lCorner()
  turtle.turnLeft()
  turtle.dig()
  forward()
  turtle.digUp()
  turtle.digDown()
  turtle.turnLeft()
end

local size, height = ...
if size == nil or height == nil then
  print("Usage: vquarry <size> <height>")
  print("Height should be a multiple of 3.")
  return
end
size = tonumber(size)
height = tonumber(height)
if height < 3 then
  print("Height must be at least 3.")
  return
end

turtle.digUp()
turtle.digDown()
for y = 3, height, 3 do
  for x = 1, size do
    xforward(size - 1)
    if x == size then
      turtle.turnRight()
      if size % 2 == 1 then
        turtle.turnRight()
      end
      if y + 3 <= height then
        for i = 1, 3 do
          up()
        end
        turtle.digUp()
      end
    elseif x % 2 == 1 then
      rCorner()
    else
      lCorner()
    end
  end
end
for y = 4, height, 3 do
  for i = 1, 3 do
    down()
  end
end