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 java.math.BigInteger

/**
 * Created by m00nlight on 7/27/15.
 */
object Main {
  def main(args: Array[String]) {
    val xs = io.Source.stdin.getLines().toList.head.split("\\s+").map(_.toInt)
    val a = new BigInt(BigInteger.valueOf(xs.head))
    val b = new BigInt(BigInteger.valueOf(xs.tail.head))
    println(a.gcd(b))
  }
}