add_action( 'save_post', 'wpse105926_save_post_callback' );

function wpse105926_save_post_callback( $post_id ) {
    $post_slug = get_post_field( 'post_name', get_post() );
    $new_slug=explode ( '-' , $post_slug );
    // verify post is not a revision
    if ( ! wp_is_post_revision( $post_id ) ) {
        // unhook this function to prevent infinite looping
        remove_action( 'save_post', 'wpse105926_save_post_callback' );
        // update the post slug
        wp_update_post( array(
            'ID' => $post_id,
            'post_name' => $new_slug[0].'-'.$new_slug[1].'-'.$new_slug[2]
        ));
        // re-hook this function
        add_action( 'save_post', 'wpse105926_save_post_callback' );
    }
}