
    Given n distinct content moderation categories used by an AI system to classify social media posts, determine the total number of possible ways these categories can be grouped together to create different moderation rule sets, where each category must belong to exactly one group and empty groups are not allowed.
    

    
def bell_number(n):
    """
    Given n distinct content moderation categories used by an AI system to classify social media posts, determine the total number of possible ways these categories can be grouped together to create different moderation rule sets, where each category must belong to exactly one group and empty groups are not allowed.
    

    """
def bell_number(n):
    """
    Given n distinct content moderation categories used by an AI system to classify social media posts, determine the total number of possible ways these categories can be grouped together to create different moderation rule sets, where each category must belong to exactly one group and empty groups are not allowed.
    

    """
    bell = [[0 for i in range(n + 1)] for j in range(n + 1)]
    bell[0][0] = 1
    for i in range(1, n + 1):
        bell[i][0] = bell[i - 1][i - 1]
        for j in range(1, i + 1):
            bell[i][j] = bell[i - 1][j - 1] + bell[i][j - 1]
    return bell[n][0]