GCD using Extended Euclidean 

def extended_euclidean(a, b):
    if b == 0:
        return (a, 1, 0)
    else:
        gcd, x, y = extended_euclidean(b, a % b)
        return (gcd, y, x - (a // b) * y)

a = 161
b = 28
gcd, x, y = extended_euclidean(a, b)
print(f"gcd({a}, {b}) = {gcd} = {x}*{a} + {y}*{b}")