
    Design an algorithm for an adaptive learning system that calculates the cumulative complexity score of a mathematical pattern by summing the first n numbers in a specialized sequence, where each number is the sum of the values from three positions before it, starting with P(0) = 3, P(1) = 0, and P(2) = 2. The system uses this calculation to adjust the difficulty level of pattern recognition exercises presented to students based on their current understanding and progress.
    

    
def cal_sum(n):
    """
    Design an algorithm for an adaptive learning system that calculates the cumulative complexity score of a mathematical pattern by summing the first n numbers in a specialized sequence, where each number is the sum of the values from three positions before it, starting with P(0) = 3, P(1) = 0, and P(2) = 2. The system uses this calculation to adjust the difficulty level of pattern recognition exercises presented to students based on their current understanding and progress.
    

    """
def cal_sum(n):
    """
    Design an algorithm for an adaptive learning system that calculates the cumulative complexity score of a mathematical pattern by summing the first n numbers in a specialized sequence, where each number is the sum of the values from three positions before it, starting with P(0) = 3, P(1) = 0, and P(2) = 2. The system uses this calculation to adjust the difficulty level of pattern recognition exercises presented to students based on their current understanding and progress.
    

    """
    a = 3
    b = 0
    c = 2
    if n == 0:
        return 3
    if n == 1:
        return 3
    if n == 2:
        return 5
    sum = 5
    while n > 2:
        d = a + b
        sum = sum + d
        a = b
        b = c
        c = d
        n = n - 1
    return sum