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 array_integer(a)
	0.upto(a.count) {|x|
		a[x] = a[x].to_i
	}
	return a
end

x,y = STDIN.gets.chomp.split(' ')
x = x.to_i
y = y.to_i

if y > x then
	v = x
	x = y
	y = v
end

while x % y != 0
	v = x % y
	x = y
	y = v
end

print y, "\n"