
    Given a patient's n distinct medical risk factors, determine the number of possible ways these factors can be grouped into different risk assessment categories to evaluate readmission probability. Each risk factor must be assigned to exactly one category, and the categories collectively must cover all risk factors, where different grouping combinations represent distinct approaches to analyzing the patient's overall readmission risk.
    

    
def bell_number(n):
    """
    Given a patient's n distinct medical risk factors, determine the number of possible ways these factors can be grouped into different risk assessment categories to evaluate readmission probability. Each risk factor must be assigned to exactly one category, and the categories collectively must cover all risk factors, where different grouping combinations represent distinct approaches to analyzing the patient's overall readmission risk.
    

    """
def bell_number(n):
    """
    Given a patient's n distinct medical risk factors, determine the number of possible ways these factors can be grouped into different risk assessment categories to evaluate readmission probability. Each risk factor must be assigned to exactly one category, and the categories collectively must cover all risk factors, where different grouping combinations represent distinct approaches to analyzing the patient's overall readmission risk.
    

    """
    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]