<image>As shown in the diagram $$①$$, two lines intersect at a single point, and there are a total of $$ \dfrac {(4-2)×4}{4}=2$$ pairs of vertically opposite angles in the diagram; in diagram $$②$$, three lines intersect at a point, and there are a total of $$ \dfrac {(6-2)×6}{4}=6$$ pairs of vertically opposite angles; in diagram $$③$$, four lines intersect at a point, resulting in $$ \dfrac {(8-2)×8}{4}=12$$ pairs of vertically opposite angles; $$…$$;  Following this pattern, if six lines intersect at a single point, then the total number of pairs of vertically opposite angles in the diagram is ______. ($$Only fill in the number$$).$$