Move last element to next line in a flex container

I have this structure in my HTML code:

<div style="display:flex"><div class="div_first">1</div><div class="div_second">2</div><div class="div_third">3</div><div class="div_next_line"><div class="div_first">4</div><div class="div_second">5</div><div class="div_third">6</div></div></div>

Is it possible to have 4 5 6 in second line with the same columns as 1 2 3, like so:

1    2    34    5    6

The structure of the HTML code cannot be changed.