t = turtle
left = 0
forward = 0
down = 0

function distance ()
	return math.sqrt(left^2 + forward^2 + down^2)
end

function go (direction)
	if direction == 'l' then
		t.turnLeft()
		st = t.dig()
		if st then st = t.forward(); t.turnRight() end
		if st then left=left+1 end
	elseif direction == 'r' then
		t.turnRight()
		st = t.dig()
		if st then st = t.forward(); t.turnLeft() end
		if st then left=left-1 end
	elseif direction == 'd' then
		t.digDown()
		st = t.down()
		if st then down=down+1 end
	elseif direction == 'u' then
		t.digUp()
		st = t.up()
		if st then down=down-1 end
	elseif direction == 'f' then
		t.dig()
		st = t.forward()
		if st then forward=forward+1 end
	elseif direction == 'b' then
		t.turnLeft()
		t.turnLeft()
		st = t.dig()
		if st then forward=forward-1 end
		t.turnLeft()
		t.turnLeft()
	end
	return st
end

function returnHome ()
	while left ~= 0 do
		if left > 0 then
			go('r')
		else
			go('l')
		end
	end
	while forward ~= 0 do
		if forward > 0 then
			go('b')
		else
			go('f')
		end
	end
	while down ~= 0 do
		if down > 0 then
			go('u')
		else
			go('d')
		end
	end
end


downLine = true
while true do
	if (distance() > 0.8 * turtle.getFuelLevel()) then
		returnHome()
		break
	end
	if (downLine) then
		st = go('d')
	else
		st = go('u')
	end
	if (~st) then
		st = go('f')
		if (~st) then
			print('got stuck')
			returnHome()
			break
		end
		downLine = false
	end
end