All the positive integers up to n$=30$ that are multiples of a$=3$ are: $3,6,9,12,15,18,$

$21,24,27$ and $30.$

All the positive integers up to n$=30$ that are multiples of b$=5$ are: $5,10,15,20,25$ and $30.$

All the positive integers up to n$=30$ that are multiples of a$=3$ OR b$=5$ are: $3,5,6,9,10,12,$

$15,18,20,21,24,25,27$ and $30.$ The sum of these multiples is $225.$

Based on this example, write a function called sum$\_$unique that returns the sum

of all the unique multiples of a OR b up to n$.$

The input arguments of the function a$,$ b$,$ n are any positive integers chosen

by the user when calling the function in the Command window, after we have

already defined it$.$