
    Design a security verification system for a mobile banking app that calculates the cumulative security score for high-value transactions. The system starts with an initial number of security checks (n) and progressively reduces the verification requirements by 2 steps until reaching the base security level. For each transaction, the system needs to compute the total security weight by adding the number of checks at each verification level, starting from n and decreasing by 2 until reaching zero or a negative value. For example, a transaction requiring 6 initial security checks would add up the checks needed at each level (6 + 4 + 2) to determine the overall security intensity. This cumulative score helps determine the appropriate biometric verification requirements for the transaction.
    

    
def sum_series(n):
    """
    Design a security verification system for a mobile banking app that calculates the cumulative security score for high-value transactions. The system starts with an initial number of security checks (n) and progressively reduces the verification requirements by 2 steps until reaching the base security level. For each transaction, the system needs to compute the total security weight by adding the number of checks at each verification level, starting from n and decreasing by 2 until reaching zero or a negative value. For example, a transaction requiring 6 initial security checks would add up the checks needed at each level (6 + 4 + 2) to determine the overall security intensity. This cumulative score helps determine the appropriate biometric verification requirements for the transaction.
    

    """
def sum_series(n):
    """
    Design a security verification system for a mobile banking app that calculates the cumulative security score for high-value transactions. The system starts with an initial number of security checks (n) and progressively reduces the verification requirements by 2 steps until reaching the base security level. For each transaction, the system needs to compute the total security weight by adding the number of checks at each verification level, starting from n and decreasing by 2 until reaching zero or a negative value. For example, a transaction requiring 6 initial security checks would add up the checks needed at each level (6 + 4 + 2) to determine the overall security intensity. This cumulative score helps determine the appropriate biometric verification requirements for the transaction.
    

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