Different template for odd and even posts

I needing to get a different template based on odd/even posts. Not sure if I need to write a function and or how to call for it in my archives.php. I need something like this:

if ( (odd numbered post) {
    get_template_part ( 'content-left' );
} else {
    get_template_part( 'content-right' );
}
?>
<?php endwhile; ?>

		<?php else : ?>
			<?php get_template_part( 'content', 'none' ); ?>