Stairs upwards

local arg = ...
local arg1 = tonumber(arg)
arg1 = arg1-1
local counter = 0
local last = ""
function placeUpLeft()
    turtle.placeUp()
    turtle.turnLeft()
    turtle.forward()
    turtle.turnRight()
end

function placeUpRight()
    turtle.placeUp()
    turtle.turnRight()
    turtle.forward()
    turtle.turnLeft()
end

function up()
    turtle.forward()
    turtle.up()
end

function back()
    if last == "left" then
        turtle.turnLeft()
    elseif last == "right" then
        turtle.turnRight()
    end
    turtle.forward()
    turtle.turnLeft()
    turtle.turnLeft()
    turtle.up()
    turtle.forward()
    if last == "left" then
        turtle.turnRight()
    elseif last == "right" then
        turtle.turnLeft()
    end
    for i=0, arg1 do
        turtle.forward()
        turtle.down()
    end
    turtle.forward()
    os.reboot()
end

for j = 1, arg1 do
    placeUpLeft()
    placeUpLeft()
    turtle.placeUp()
    last = "left"
    up()
    counter = counter + 1
    print(counter)
    if counter > arg1 then
        print("Back()")
        back()
    end
    placeUpRight()
    placeUpRight()
    turtle.placeUp()
    last = "right"
    up()
    counter = counter + 1
    print(counter)
    if counter > arg1
then
        print("Back()")
        back()
    end
end