After you do the change to use `vector<RCP<Integer>>`, then this line just becomes:
```
assert(divides(a, *it) == true)
```
But for this to work, you also need to change
```
void _test_primefactors(const Integer &a, unsigned size)
```
to
```
void _test_primefactors(const RCP<Integer> &a, unsigned size)
```