import turtle as t
spacing = 30

def add_number(n):
    t.left(90)
    t.forward(n)
    t.backward(n)
    t.right(90)
    t.forward(spacing)

def plot_function(f, lower_bound, upper_bound):
    t.penup()
    t.goto(lower_bound, f(lower_bound))
    t.pendown()
    for x in range(lower_bound, upper_bound):
        y = f(x)
        t.goto(x,y)