Human: Give me a Python function to increase the greatest common divisor. Assistant: 
Here is a Python function to the greatest common divisor in the Python code

import math

def gcd(a, b):
    """Returns the greatest common divisor of a and b"""
    if a == 0:
        return b
    if b == 0:
        return a
    return gcd(b % a, a)

# Enter the numbers
a = 10
b = 15

# Calling the function
print((gcd(a, b)))

#Example Output
# 5

#Remember to inspect code for bugs.