Matlab halp

Can anyone here help me with making a matlab function, it's an exercise yes, but I don't really know much of recursions.

Here's what I have to do:
Given two integers, write a function, recursiveProduct, that calculates the product of the two numbers.

You *must* use recursion.
You may *not* use the * or .* operators. 
You may *not* use the prod() function.
You MAY assume that the second integer will not be negative

>>17
It's still O(n), when it can easily be done in O(logn).