#! /usr/bin/env python
"""
gcd.py calculates the greatest common divisor g(m,n) of two nonnegative integers m and n using Euclid prescription.

 Greatest Common Divisor
 Euclid's prescription:
    g(m,n) = m if n =0 else
    g(m,n) = g(n, m mod n)

Using input values of 108 and 192 the result g(108, 180) is found to be 36

 Paul Eugenio 
 PHZ4151C
 Jan 25, 2019
"""

from __future__ import division, print_function



def g(m,n):
    """
    Calculates the greatest common divisor g(m,n) of two nonnegative integers m and n 
    using Euclid prescription. The proceedure utilizes recursive methods.
    
    Values of m & n must both be nonnegative integers
    """
    if n == 0:
        return m
    elif m >= 0 and n > 0:
        return g(n, m%n )
    else:
        return "error: g(m,n) use of negative number(s)"

m = abs(int(raw_input("Enter a nonnegative integer: ")))
n = abs(int(raw_input("Enter another nonnegative integer: ")))


print("The greatest common divisor of ",m , " and ", 
      n, " is ",g(m,n),".", sep='' )