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: Accepted)

def gcd( x, y )
	if 0 == y
		return x
	else
		return gcd( y, x%y )
	end	
end

a, b = gets.split( " " ).map { |val| val.to_i }
if a < b
	a, b = b, a
end
puts( gcd( a, b ) )