def return_sign(i, m, n, r):
    """
        Helper function, creates a three-piece step function

        :param i: Value to compare
        :type i: int
        :param m: Middle value
        :type m: int
        :param n: Left extreme value
        :type n: int
        :param r: Right extreme value
        :type r: int

        :returns: int -- Three-piece sign
    """
    if i <= n - m:
        return 1
    elif i <= r:
        return 0
    else:
        return -1
