Maximize min distance = binary search on answer m. Check: can k teleports cover all friends within distance m? Each teleport covers a contiguous interval.

Sort friends. Greedy: place teleport at friend_pos + m, skip all friends within m of it. Count teleports needed; if ≤ k, m is feasible.

Friends at 0 and x limit teleport placement. Gaps between consecutive friends after sorting — available positions for teleports in each gap is max(0, gap_width - 2m + 1).