## Objective

Create a function to find the greatest common divisor of two integers.

Easy

## Description

The greatest common divisor, or simply the gcd, of two non-negative integers $a$ and $b$ is the largest integer that divides both $a$ and $b$.

For instance, the greatest common divisor of $10$ and $20$ is $10$. This is often written as $\text{gcd}(10, 20) = 10$. All common divisors of $10$ and $20$ are $1, 2, 5, 10$, where the largest value is $10$. Hence, $\text{gcd}(10, 20) = 10$.

Similarly, $\text{gcd}(10, 3) = 1$. There is no common divisor of $10$ and $3$ except for $1$, hence, it's the greatest common divisor. Such a pair of integers whose gcd is $1$ are said to be relatively prime to each other.

As another example, $\text{gcd}(10, 0) = 10$. On the same lines, $\text{gcd}(0, 10) = 10$ as well. However, $\text{gcd}(0, 0)$ is undefined. Every integer can divide $0$, and so likewise there is no limit to this expression.

In this exercise, you have to create a function gcd() that takes in two integers as arguments and returns back their gcd. If both the numbers are 0, the function should return INF.

You MUST implement a brute force algorithm using for that goes over every integer to see if it's a common divisor or not.

Here's an example of the usage of the function:

<?php

echo 'gcd(10, 20): ', gcd(10, 20), "\n";
echo 'gcd(20, 20): ', gcd(20, 20), "\n";
echo 'gcd(10, 0): ', gcd(10, 0), "\n";
echo 'gcd(0, 10): ', gcd(0, 10), "\n";
echo 'gcd(0, 0): ', gcd(0, 0), "\n";
gcd(10, 20): 10 gcd(20, 20): 20 gcd(10, 0): 10 gcd(0, 10): 10 gcd(0, 0): INF