tt

length = 6
width = 5
height = 5

-- getting the neccessary amount of fuel
success = turtle.refuel(math.ceil(length * height * width / 160))
if not success then
    print("place the fuel to the active slot")
    exit()
end

-- [[ main code ]] --
length = length - 1
width  = width  - 1
height = height - 1

h = 0
repeat
    local j = 0
    repeat
        local i = 0
        repeat
            turtle.dig()
            turtle.forward()
            i = i + 1
        until (h % 2 == 0 and i >= width) or (h % 2 ~= 0 and i >= length)

        if j % 2 == 0 and ((h % 2 == 0 and j < length) or (h % 2 ~= 0 and j < width)) then
            turtle.turnLeft()
            turtle.dig()
            turtle.forward()
            turtle.turnLeft()
        elseif ((h % 2 == 0 and j < length) or (h % 2 ~= 0 and j < width)) then
            turtle.turnRight()
            turtle.dig()
            turtle.forward()
            turtle.turnRight()
        end

        j = j + 1

    until (h % 2 == 0 and j >= length + 1) or (h % 2 ~= 0 and j >= width + 1)

    turtle.digDown()
    turtle.down()
    if h % 2 == 0 then
        if width % 2 == 0 then
            turtle.turnLeft()
        else
            turtle.turnRight()
        end
    else
        if width % 2 == 0 then
            turtle.turnRight()
        else
            turtle.turnLeft()
        end
    end
    h = h + 1
until h == height