#include <bits/stdc++.h>
using namespace std;
using ll = long long;

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	int n, L, k;
	cin >> n >> L >> k;
	vector<int> a(n + 2);
	for(int i = 1; i <= n; i++) cin >> a[i];
	a[n + 1] = L;
	n += 2;
	// n + 1 -> k + 1
	// n - k 回の合体で大きいものを2つ作る問題
	int ok = 0, ng = L + 1;
	while(ok + 1 < ng){
		int mid = (ok + ng) / 2;
		vector<array<int,2>> dp(n, {-(1 << 30), -(1 << 30)});
		for(int l = 0, r = 0; l < n; l++){
			if(l + 1 < n){
				dp[l + 1][0] = max(dp[l + 1][0], dp[l][0] + 1);
				dp[l + 1][1] = max(dp[l + 1][1], dp[l][1] + 1);
			}
			while(r < n && a[r] - a[l] < mid) r++;
			if(r < n){
				dp[r][0] = max(dp[r][0], l + 1);
				dp[r][1] = max(dp[r][1], dp[l][0] + 1);
			}
		}
		(dp[n - 1][1] >= k + 1 ? ok : ng) = mid;
	}
	cout << ok << '\n';
}