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 PHP (judge verdict: Accepted)

<?php
// Your code here!
   function gcb( $max, $min )
{
	while( 0 != $min ) {
		$n = $min;
		$min = $max%$min;
		$max = $n;
	
	}
	
	return $max;
}

	$nums = explode( " ", trim( fgets( STDIN ) ) );
	$max = intval(max( $nums ));
	$min = intval(min( $nums ));
	echo gcb($max, $min);
?>