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
fscanf(STDIN, "%d %d", $num1, $num2);

$div = 0;
$max_num = max($num1, $num2);
$min_num = min($num1, $num2);
while ($min_num != 0) {
    $tmp = $min_num;
    $min_num = $max_num % $min_num;
    $max_num = $tmp;
}

echo $max_num."\n";
?>