import math


def get_Rost_ID_threshold(L, n=0):
    """
    This function returns the Rost sequence identity threshold for a
    given alignment of length "L".

    @input:
    L {int} alignment length
    parameter {int} N parameter in the curve (if > 0 more strict)
    @return: {Decimal}
        
    """

    return n+ (480*pow(L,float('-0.32')*(1+pow(float(repr(math.e)),float(repr(float(-L)/1000))))))