#include<iostream>
#include<algorithm>
using namespace std;
int main() {
	long long l = 0, r = 0, ans = 0, t, M, N, i, distance[50005] = { 0 }, gap[50005] = { 0 },m;
	long long g, L;
	cin >> L >> N >> M;
	for (i = 1; i <= N; i++) {
		cin >> distance[i];
		gap[i] = distance[i] - distance[i - 1];
	}
	gap[N + 1] = L-distance[N];
	r = L;
	l = 1;
	while (l<=r) {
		m = 0;
		g = 0;
		t = (l + r) / 2;
		for (i = 1; i <= N+1; i++) {
			g += gap[i];
			if (g >= t)
				g = 0;
			else
				m++;
		}
		if (m == M) {
			ans = t;
			l = t + 1;
		}
		else if (m > M) {
			r = t - 1;
		}
		else
			l = t + 1;

	}
	cout << ans;
}

8 9 10三组数据是WA 请问各位神犇我这里有哪些地方有问题嘞qwq