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 euclid(a, b)
  while a > 0
    if b == 0
      return a
    else
      return euclid(b, a%b)
    end
  end
end
 
 
num1, num2 = gets.chomp.split.map(&:to_i)
puts euclid(num1, num2)