def gcd(a,b):
if b == 0:
return a
return gcd(b, a % b)

def gcd(a, b):
if a < b:
a, b = b, a
while b != 0:
a, b = b, a%b
return b

def gcd(a,b):
if b == 0:
return a
return gcd(a, a % b)

def gcd(a,b):
if b == 0:
return a
return gcd(b, b % a)