• 辗转相除法:取模运算性能较差，时间复杂度近似为O(log(max(a,b)))
  • 更相减损术：算法性能不稳定，最坏为O(max(a,b))
  • 更相减损术与移位相结合：性能稳定，时间复杂度为O(log(max(a,b)))
    def gcd(a, b):
  if a == b: return a 
  if a < b : a,b = b,a
  if a&1 == 0 and b&1 == 0:
      return gcd(a>>1,b>>1) <<1
  elif a&1 == 0 and b&1 != 0:
      return gcd(a>>1,b)
  elif a&1 != 0 and b&1 == 0:
      return gcd(a,b>>1)
  else:
      return gcd(b, a-b)
m, n = map(int, input().split())
print(gcd(m, n))