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 Ruby (judge verdict: Time Limit Exceeded)

x, y = gets.chomp.split.map(&:to_i).sort
mod = y % x
ary = Array.new
if x == y
	puts x
else
	loop do
		if (y % x) % mod == 0 && x % mod == 0
			puts mod
			break
		else
			mod -= 1
		end
	end
end