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: n = input().split()
  x = int(n[0])
  y = int(n[1])
  if 1 <= x < 1000000000 and 1 <= y <= 1000000000:
      if x > y:
          while y != 0:
              t = y
              y = x % t
              x = t
          print(x)
      else:
          while x != 0:
              t = x
              x = y % t
              y = t
          print(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"}]