output_description: Output the greatest common divisor of _a_ and _b_.
input_description: _a_ and _b_ are given in a line sparated by a single space.
attempt: # -*- coding: utf-8 -*-
  
  import sys
  
  if sys.version_info.minor >= 5:
      from math import gcd
  else:
      from fractions import gcd
  
  
  def input():
      return sys.stdin.readline().strip()
  
  
  def list2d(a, b, c):
      return [[c] * b for i in range(a)]
  
  
  def list3d(a, b, c, d):
      return [[[d] * c for j in range(b)] for i in range(a)]
  
  
  def ceil(x, y=1):
      return int(-(-x // y))
  
  
  def INT():
      return int(input())
  
  
  def MAP():
      return map(int, input().split())
  
  
  def LIST():
      return list(map(int, input().split()))
  
  
  def Yes():
      print("Yes")
  
  
  def No():
      print("No")
  
  
  def YES():
      print("YES")
  
  
  def NO():
      print("NO")
  
  
  sys.setrecursionlimit(10**9)
  INF = float("inf")
  MOD = 10**9 + 7
  
  x, y = MAP()
  print(gcd(x, y))
  
problem_description: Greatest Common Divisor
  
  Write a program which finds the greatest common divisor of two natural numbers
  _a_ and _b_
samples: [{"input": "54 20", "output": "2"}, {"input": "147 105", "output": "21"}]