calculate a power with Storyline

Hi !

I would like to calculate a power with Storyline. I mean I would like to calcule 4 power 2 = 16. I know I can do it with triggers for a known number (4 power 2 in this case, doing 4 * 4). But with a number given by the user (using variables), I don't know. 

Do you have any idea ?

Thank you!