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
$number = fgets(STDIN);
$numbers = explode(" " , $number);

$num1 = trim($numbers[0]);
$num2 = trim($numbers[1]);

$min_num = min($num1, $num2);

if ($num1 < $num2) {
	$hoge = $num1;
	$num1 = $num2;
	$num2 = $hoge;
}

while ($num2 > 0):
	$r = $num1 % $num2;
	$num1 = $num2;
	$num2 = $r;
endwhile;

echo $num1 . PHP_EOL;