
    Given n delivery zones in a city, determine the number of unique ways to assign these zones among available delivery drivers, where each driver must be assigned at least one zone and each zone must be assigned exactly once. Each possible assignment combination represents a valid partitioning of the delivery network, accounting for current traffic and weather conditions.
    

    
def bell_number(n):
    """
    Given n delivery zones in a city, determine the number of unique ways to assign these zones among available delivery drivers, where each driver must be assigned at least one zone and each zone must be assigned exactly once. Each possible assignment combination represents a valid partitioning of the delivery network, accounting for current traffic and weather conditions.
    

    """
def bell_number(n):
    """
    Given n delivery zones in a city, determine the number of unique ways to assign these zones among available delivery drivers, where each driver must be assigned at least one zone and each zone must be assigned exactly once. Each possible assignment combination represents a valid partitioning of the delivery network, accounting for current traffic and weather conditions.
    

    """
    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]