steps = 0

function dig()

if turtle.getFuelLevel() < 3 then
        for i = 1,16 do
                if turtle.getItemCount(i) > 0 then
                        turtle.select(i)
                        if turtle.refuel(1) then
                                break
                        end
                end
        end
        turtle.select(1)
end

while true do
	if turtle.detect() == true then
		turtle.dig()
	else
		break
	end
	sleep(0.4)
end
	turtle.forward()
while true do
	if turtle.detectUp() == true then
	turtle.digUp()
else
break
end
sleep(0.4)
end

end

function returns()
	turtle.turnRight()
	turtle.turnRight()
	for i = 1, steps do
		turtle.forward()
	end
end

function start()
io.write "how long do you want to tunnel ?"
steps = io.read()
steps = tonumber(steps)
end

start()

for i = 1, steps do
	dig()
end

returns()