def init(total_steps):
    """
    Initialize the world coordinates and draw labels.  The lower left
    is (-1,-1) and the upper right is computed based on the total
    number of steps.

        total_steps (int): a non-negative, even value for the total
            number of steps in one, up-down staircase
    """

    title("Uniform stairs")
    setworldcoordinates(-1, -1, total_steps*2+2, total_steps*2+2)
    pensize(3)
    up()
    setpos(0, total_steps//2+1)
    down()
    write("Iterative", font=("Arial", 20, "bold"))
    up()
    setpos(total_steps+1, total_steps//2+1)
    down()
    write("Recursive", font=("Arial", 20, "bold"))
    up()
    home()