def dup_rshift(f, n, K):
    """
    Efficiently divide ``f`` by ``x**n`` in ``K[x]``.

    Examples
    ========

    >>> R, x = ring('x', ZZ)

    >>> R.dup_rshift(x**4 + x**2, 2)
    x**2 + 1
    >>> R.dup_rshift(x**4 + x**2 + 2, 2)
    x**2 + 1

    """
    return f[:-n]
