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: Wrong Answer)

x, y = gets.chomp.split.map(&:to_i)

if x >= y
   rest = x % y
   y_common_divisors = Array.new
   for i in 1..y do
      y_common_divisors.push i if y % i == 0
   end
   x_y_common_divisors = Array.new
   for i in 1..rest do
      x_y_common_divisors.push i if rest % i == 0
   end

   common_divisors = y_common_divisors & x_y_common_divisors
   puts common_divisors[common_divisors.count - 1]
else
   rest = y % x
   x_common_divisors = Array.new
   for i in 1..x do
      x_common_divisors.push i if x % i == 0
   end
   x_y_common_divisors = Array.new
   for i in 1..rest do
      x_y_common_divisors.push i if rest % i == 0
   end

   common_divisors = x_common_divisors & x_y_common_divisors
   puts common_divisors[common_divisors.count - 1]
end