def gcd(a, b):
if a == 0:
return b
while b != 0:
if a > b:
a -= b
elif b > a:
b -= a
return a
gcd(1989, 867)
ZGVmIGdjZChhLCBiKToKICAgIGlmIGEgPT0gMDoKICAgICAgICByZXR1cm4gYgogICAgd2hpbGUgYiAhPSAwOgogICAgICAgIGlmIGEgPiBiOgogICAgICAgICAgICBhIC09IGIKICAgICAgICBlbGlmIGIgPiBhOgogICAgICAgICAgICBiIC09IGEKICAgIHJldHVybiBhCgpnY2QoMTk4OSwgODY3KQ==