
    In a content moderation system with n distinct classification levels, determine how many different ways content items can be arranged such that exactly m items have a higher risk classification than the item that follows them. The classification levels range from safe (0) to most harmful (n-1), and each level must be used exactly once in the arrangement.
    

    
def eulerian_num(n, m):
    """
    In a content moderation system with n distinct classification levels, determine how many different ways content items can be arranged such that exactly m items have a higher risk classification than the item that follows them. The classification levels range from safe (0) to most harmful (n-1), and each level must be used exactly once in the arrangement.
    

    """
def eulerian_num(n, m):
    """
    In a content moderation system with n distinct classification levels, determine how many different ways content items can be arranged such that exactly m items have a higher risk classification than the item that follows them. The classification levels range from safe (0) to most harmful (n-1), and each level must be used exactly once in the arrangement.
    

    """
    if m >= n or n == 0:
        return 0
    if m == 0:
        return 1
    return (n - m) * eulerian_num(n - 1, m - 1) + (m + 1) * eulerian_num(n - 1, m)