
    Design a learning path calculator that determines the total skill points a student can earn while working through adaptive difficulty levels. Starting from the highest difficulty level n, the system automatically adjusts by decreasing the difficulty by 2 levels at a time until reaching the student's baseline competency (where remaining levels become non-contributory). For each difficulty level in this progression, students earn points equal to the current difficulty value, and these points need to be summed to determine the total potential skill points available in their personalized learning path. The calculator should work for any initial difficulty level n, creating paths that systematically step down in complexity until reaching or dropping below the student's starting point.
    

    
def sum_series(n):
    """
    Design a learning path calculator that determines the total skill points a student can earn while working through adaptive difficulty levels. Starting from the highest difficulty level n, the system automatically adjusts by decreasing the difficulty by 2 levels at a time until reaching the student's baseline competency (where remaining levels become non-contributory). For each difficulty level in this progression, students earn points equal to the current difficulty value, and these points need to be summed to determine the total potential skill points available in their personalized learning path. The calculator should work for any initial difficulty level n, creating paths that systematically step down in complexity until reaching or dropping below the student's starting point.
    

    """
def sum_series(n):
    """
    Design a learning path calculator that determines the total skill points a student can earn while working through adaptive difficulty levels. Starting from the highest difficulty level n, the system automatically adjusts by decreasing the difficulty by 2 levels at a time until reaching the student's baseline competency (where remaining levels become non-contributory). For each difficulty level in this progression, students earn points equal to the current difficulty value, and these points need to be summed to determine the total potential skill points available in their personalized learning path. The calculator should work for any initial difficulty level n, creating paths that systematically step down in complexity until reaching or dropping below the student's starting point.
    

    """
    if n < 1:
        return 0
    else:
        return n + sum_series(n - 2)