local args = {...}

if #args ~= 1 then
	print("Usage: tunnel <distance>")
else
	local torches = math.floor(args[1] / 8)
	print("Put "..torches.." torches in slot 1, then press enter.")
	read()
end

function dig()
	while turtle.detect() do turtle.dig() end
end

function digUp()
	while turtle.detectUp() do turtle.digUp() end
end

function pokeHole()
	for i=1,5 do
		dig()
		if i < 5 then
			turtle.forward()
		end
	end
	for i=1,4 do
		turtle.back()
	end
end

for i=1,args[1] do
	dig()
	turtle.forward()
	digUp()
	if i%4 == 0 then
		turtle.up()
		turtle.turnLeft()
		pokeHole()
		turtle.turnRight()
		turtle.turnRight()
		pokeHole()
		turtle.turnLeft()
		turtle.down()
	end
	if i%8 == 7 then
		turtle.back()
		turtle.select(1)
		turtle.placeUp()
	end
end