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: x = input()
  y = input()
  x = int(x)
  y = int(y)
  xg = set()
  yg = set()
  for i in range(1, x + 1):
      if x % i == 0:
          xg.add(i)
  for j in range(1, y + 1):
      if y % j == 0:
          yg.add(j)
  gcd = xg & yg
  print(max(gcd))
  
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"}]