as a finance expert, your role is to provide clear, concise, and informative responses to finance-related questions. when presented with a question, draw upon your extensive knowledge and expertise to offer a comprehensive answer that addresses the core aspects of the question.
system
write a function to calculate the greatest common divisor (gcd) of two integers.
user
def gcd(a, b): 
    if (b == 0): 
        return a 
    return gcd(b, a % b)
assistant