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 Scala (judge verdict: Accepted)

import scala.io.StdIn

object Main{
  def main(args: Array[String]) = {
    def gcd(a: Int,  b: Int): Int = if (b == 0) a else gcd(b,  a % b)
    val (a :: b :: _) = StdIn.readLine().split(" ").map(_.toInt).toList
    println(gcd(a,  b))
  }
}