bq. Given n a prime number and p, q two integer numbers between 0 and n-1 find k such that  p^k^ = q modulo n.
This problem can be solved using the baby step, giant step algorithm which uses the meet in the middle trick.

We can write k = $i sqrt(n) + j$

We can write k = $i([sqrt(n)] + 1) + j$

Notice that $i <= sqrt(n)$ and $j <= sqrt(n)$.
Now our equality looks like this $p^(i ([sqrt(n)] + 1) + j)^ = q modulo n$.
We can divide by $p^j^$ and get $p^(i[sqrt(n)] + 1)^ = qp^-j^ modulo n$.