Intersection of two arrays

You are given two arrays $a$ and $b$. Find all distinct numbers present in both, in increasing order.

The first line contains $n$, the second the array $a$. The third line contains $m$, the fourth the array $b$. $1 \le n, m \le 10^5$, $|a_i|, |b_i| \le 10^9$.

The first line contains the number of common values $k$. The second line contains those $k$ numbers in increasing order (empty if $k = 0$).

Turn both arrays into sets and take the intersection (Python — a & b). Repetitions count once: in the first example $2$ occurs twice in both arrays but once in the answer — 2 5.

For $n = 10^5$ comparing every element with all others ($n^2 = 10^{10}$ operations) is too slow — a set or a dictionary does it in one pass.