Problem:
Greatest Common Divisor

Write a program which finds the greatest common divisor of two natural numbers a and b

Input

a and b are given in a line sparated by a single space.

Output

Output the greatest common divisor of a and b.

Constrants

1 ≤ a, b ≤ 109

Hint

You can use the following observation:

For integers x and y, if x ≥ y, then gcd(x, y) = gcd(y, x%y)

Sample Input 1

54 20

Sample Output 1

2

Sample Input 2

147 105

Sample Output 2

21

Solution in Python (judge verdict: Accepted)

x,y=map(int,raw_input().split())
a=0
if x<y:
	x,y=y,x

while True:
	a=x%y
	if a==0:
		a=y
		break
	elif x%a==0 and y%a==0:
		break
	x=y
	y=a
	
print a