import math


def AUC_SE_calc(AUC, P, N):
    """
    Calculate AUC standard error.

    :param AUC: AUC value
    :type AUC: float
    :param P: number of actual positives
    :type P: int
    :param N: number of actual negatives
    :type N: int
    :return: standard error as float
    """
    try:
        q0 = AUC * (1 - AUC)
        q1 = (AUC / (2 - AUC)) - AUC**2
        q2 = ((2 * (AUC**2)) / (1 + AUC)) - AUC**2
        result = math.sqrt((q0 + (N - 1) * q1 + (P - 1) * q2) / (P * N))
        return result
    except Exception:
        return "None"