#include<iostream>
using namespace std;
typedef int ll;
ll lon, n, k, l, r;
ll a[200020];
int main() {
	cin >> lon >> n >> k;
	for (ll i = 0; i < n; i++) {
		cin >> a[i];
	}
	l = 1, r = lon;
	while (l <= r) {
		ll mid = (l + r) >> 1;
		ll sum = 0;
		for (ll i = 1; i < n; i++) {
			if (a[i] - a[i - 1] > mid) {
				sum += (a[i] - a[i - 1]) / mid;
			}
		}
		if (sum > k) {
			l = mid + 1;
		} else {
			r = mid - 1;
		}
	}
	cout << l;
	return 0;
}

请巨佬帮帮忙