{% set primaryCategory = entry.categories.level(3).first %}
            {% if primaryCategory is empty %}
                {% set primaryCategory = entry.categories.level(2).first %}
            {% endif%}
            {% if primaryCategory is empty %}
                {% set primaryCategory = entry.categories.level(1).first %}
            {% endif%}

{% set category = entry.categories.last() %}

{% set level = 0 %}
{% for category in entry.categories %}
    {% set level = category.level > level ? category.level : level %}
{% endfor %}
{% set category = entry.categories.level(level).first %}