Find the greatest common divisor (GCD) of two integers

Find the greatest common divisor (GCD) of two integers.
def gcd(a, b):

       low  = min(a, b)
       high = max(a, b)

       if low == 0:
               return high
       elif low == 1:
               return 1
       else:
               return gcd(low, high % low)

# test
N, M = 12, 14
print(gcd(N, M))       # 2
def gcd_01(a, b):
    return a if b == 0 else gcd_01(b, a % b)

# test
N, M = 1680, 640
print(gcd_01(N, M))   # 80
def gcd_02(a, b):
    if a == b:
        return a
    elif a > b:
        return gcd_02(a - b, b)
    elif a < b:
        return gcd_02(a, b - a)

# test
N, M = 1680, 640
print(gcd_02(N, M))    # 80