Ceiling

local width = 61

local torches = 2

local function refuel()
    if turtle.getFuelLevel() == 0 then
        local prev = turtle.getSelectedSlot()
        turtle.select(1)
        if not turtle.refuel(1) then
            print('Need more fuel')
            while not turtle.refuel(1) do
                sleep(1)
            end
        end
        turtle.select(prev)
    end
end

local function checkForTorch(x)
    if (x+2) % 6 == 0 then
        turtle.digUp()
        turtle.placeUp()
    end
end

turtle.select(torches)

for i = 1, width do
    refuel()
    checkForTorch(i)
    turtle.forward()
end