proplem with jquery code when i add a selector

proplem with jquery code when i add a selector

hello
i have a proplem with this code when i add my selector #nav

  1.   $(function() {
        $
    ("#nav ul > li").hover(function() {
          $
    (this).find("ul").stop(true, true).fadeIn('fast');
        
    }, function() {
          $
    (this).find("ul").stop(true, true).fadeOut('fast');
        
    });
      
    });
but

when i remove my selector #nav  it's work

  1.   $(function() {
        $
    ("ul > li").hover(function() {
          $
    (this).find("ul").stop(true, true).fadeIn('fast');
        
    }, function() {
          $
    (this).find("ul").stop(true, true).fadeOut('fast');
        
    });
      
    });
some help please