====== 제자리 멀리뛰기 ======

===== 풀이 =====
  * [[ps:problems:programmers:43236]]과 동일한 문제. 풀이는 그쪽 참고.

===== 코드 =====
<dkpr py>
"""Solution code for "BOJ 6209. 제자리 멀리뛰기".

- Problem link: https://www.acmicpc.net/problem/6209
- Solution link: http://www.teferi.net/ps/problems/boj/6209

Tags: [Parametric Search]
"""

import sys
from teflib import binsearch


def main():

    def is_valid(min_dist):
        prev_rock = 0
        removed_rock_count = 0
        for rock in rocks:
            if rock - prev_rock < min_dist:
                removed_rock_count += 1
            else:
                prev_rock = rock
        if d - prev_rock < min_dist:
            removed_rock_count += 1
        return removed_rock_count <= m

    d, n, m = [int(x) for x in sys.stdin.readline().split()]
    rocks = [int(sys.stdin.readline()) for _ in range(n)]

    rocks.sort()
    print(binsearch.maximum_valid_integer(0, d // (n - m + 1) + 1, is_valid))


if __name__ == '__main__':
    main()
</dkpr>
  * Dependency: [[:ps:teflib:binsearch#maximum_valid_integer|teflib.binsearch.maximum_valid_integer]]

{{tag>BOJ ps:problems:boj:골드_2}}