
    At a complex urban intersection, determine the number of unique ways to organize different traffic flow patterns into distinct signal phases, where each phase can contain one or more compatible vehicle movements. Given n possible traffic movements through the intersection, calculate how many different ways these movements can be grouped into valid signal timing configurations, where each movement must be assigned to exactly one phase.
    

    
def bell_number(n):
    """
    At a complex urban intersection, determine the number of unique ways to organize different traffic flow patterns into distinct signal phases, where each phase can contain one or more compatible vehicle movements. Given n possible traffic movements through the intersection, calculate how many different ways these movements can be grouped into valid signal timing configurations, where each movement must be assigned to exactly one phase.
    

    """
def bell_number(n):
    """
    At a complex urban intersection, determine the number of unique ways to organize different traffic flow patterns into distinct signal phases, where each phase can contain one or more compatible vehicle movements. Given n possible traffic movements through the intersection, calculate how many different ways these movements can be grouped into valid signal timing configurations, where each movement must be assigned to exactly one phase.
    

    """
    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]