
    In a student retention tracking system, administrators need to calculate the cumulative impact of declining student engagement across academic terms. Starting with an initial cohort size, each subsequent term shows a decrease of two students from the previous term's engagement level, continuing until no actively engaged students remain. The system needs to sum up the number of engaged students across all these terms to quantify the total student-terms of engagement. This calculation helps identify critical intervention points by tracking the pattern from full enrollment to the point where engagement reaches zero. For example, if starting with 7 students, the system would sum 7 + 5 + 3 + 1 to understand the total student-term engagement pattern.
    

    
def sum_series(n):
    """
    In a student retention tracking system, administrators need to calculate the cumulative impact of declining student engagement across academic terms. Starting with an initial cohort size, each subsequent term shows a decrease of two students from the previous term's engagement level, continuing until no actively engaged students remain. The system needs to sum up the number of engaged students across all these terms to quantify the total student-terms of engagement. This calculation helps identify critical intervention points by tracking the pattern from full enrollment to the point where engagement reaches zero. For example, if starting with 7 students, the system would sum 7 + 5 + 3 + 1 to understand the total student-term engagement pattern.
    

    """
def sum_series(n):
    """
    In a student retention tracking system, administrators need to calculate the cumulative impact of declining student engagement across academic terms. Starting with an initial cohort size, each subsequent term shows a decrease of two students from the previous term's engagement level, continuing until no actively engaged students remain. The system needs to sum up the number of engaged students across all these terms to quantify the total student-terms of engagement. This calculation helps identify critical intervention points by tracking the pattern from full enrollment to the point where engagement reaches zero. For example, if starting with 7 students, the system would sum 7 + 5 + 3 + 1 to understand the total student-term engagement pattern.
    

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