import math


def PSucLB(sigma,n,d,param):
    """ Compute the lower bound given by Theorem 2 in the paper.
    param corrersponds to Rmax in the paper.
    """
    sigma = sigma**2
    return .5 + (d*sigma)/(2*n*param) - math.exp(-param/(2*sigma))*(1+(2*sigma)/param)