If featured or latest entry
You could try this

{% set featured = craft.entries.section('blog').featured(1).count() %}
{% paginate craft.entries.section('blog').limit(12) as entriesOnPage %}
{% for index, entry in entriesOnPage %}
    {# entry is featured or it's the first entry and there are no other
    featured entries #}
    {% if entry.featured or (index == 0 and featured == 0) %}
        [markup A]
    {% else %}
        [markup B excluding featured item]
    {% endif %}
{% endfor %}