Roof+

local slot = 1
turtle.select(slot)

function Ensure()
    if turtle.getItemCount(slot) == 0 then
        slot = slot + 1
        if slot == 17 then slot = 1 end
        turtle.select(slot)
        if turtle.getItemCount(slot) == 0 then
            print("Insert more >>")
            read()
        end
    end
end

function F()
    Ensure()
    turtle.placeDown()
    turtle.forward()
end

function U()
    turtle.up()
end

function L()
    turtle.turnLeft()
end

function R()
    turtle.turnRight()
end

function FMax()
    while not turtle.detect() do
        F()
    end
end

turtle.forward()
turtle.down()
turtle.turnLeft()
turtle.turnLeft()
--
local count = 0
while true do
    while turtle.back() do
        Ensure()
        turtle.place()
        count = 0
    end
    turtle.turnRight()
    count = count + 1
    if count == 3 then
        U()
        Ensure()
        turtle.placeDown()
        break
    end
end