help with toggle

help with toggle

i am tryingo to do a list and do toggle on it

it works wrell but even when i click on li makes the toggle
is that a way to make works only on the ul???
thanks fot the help and sorry for the english.

$(function(){
      $('.a').hide();
            $('.b').click(function(){
            $(this).find('.b').next().toggle();
            });
});

<ul class='b'>123
<li class='a'>a</li>
<li class='a'>b</li>
<li class='a'>c</li>
</ul>