Query and Post limit

Hello,
i have this query

<?php $query = new WP_Query( 'cat=-3,-8' ); ?>
 <?php if ( $query->have_posts() ) : while ( $query->have_posts() ) : $query->the_post(); ?>

          <div class="blogSidebar">
            <h5><?php echo get_the_title(); ?></h5>
   <?php my_excerpt(veryshort);?>
           <a href="<?php echo get_permalink(); ?>">Read More</a>
          </div>

 <?php endwhile;
 wp_reset_postdata();
 else : ?>
 <p><?php _e( 'Sorry, no posts matched your criteria.' ); ?></p>
 <?php endif; ?>

But how can i limit just to show 1 last post? Tehere were some argument ebfore showpost ?