local btogo = 2000	--legth of the tunnel.
local b = 0			--blocks walked.
local tb = 0		-- blocks until next torch.
local t = turtle.getItemCount(16)
local i = 0
local is = 15

--loop to line 39.
repeat

--fuel.
if btogo * 4 > turtle.getFuelLevel() then print("Need more fuel!")
	end

--digging.
	turtle.dig()
	turtle.forward()
	turtle.digUp()
	turtle.digDown()
b = b + 1

-- Torch placement.
tb = tb + 1

	if tb == 9 then
		turtle.back()
		end
	if tb == 9 then
		turtle.select(16)
		end
	if tb == 9 then
		turtle.placeUp()
		end
	if tb == 9 then
		turtle.select(1)
		end
	if tb == 9 then
		tb = 0
		end

--Inventory Management.
i = i + 1
	if i == 100 then
		turtle.select(15)
		end
	if i == 100 then
		turtle.placeDown()
		end
	if i == 100 then
		turtle.select(1)
		end

	if i == 100 then
		repeat

		if i == 100 then
			is = is - 1
			end

		if i == 100 then
			turtle.select(is)
			end
		if i == 100 then
			turtle.dropDown()
			end

		until is == 1
	end

	if i == 100 then
	is = 15
	end

	if i == 100 then
		i = 0
		end


until b == btogo