#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

int N, L;
int K;
vector<int> a;

bool check(int x) {
    // dp[j][i]... maximum number of intervals taken so far,
    // guaranteeing at least j intervals of length >= x,
    // currently focusing on the i-th cut point
    vector<vector<int>> dp(4, vector<int>(N + 2, -1));
    dp[0][0] = 0;
    for (int j = 0; j < 3; j++) {
        for (int i = 0; i <= N; i++) {
            if (dp[j][i] == -1) continue;
            // take the next interval immediately
            dp[j][i + 1] = max(dp[j][i + 1], dp[j][i] + 1);

            // jump to the interval where length >= x
            int idx = (int)(lower_bound(a.begin(), a.end(), a[i] + x) - a.begin());
            if (idx >= (int)a.size()) continue;
            dp[j + 1][idx] = max(dp[j + 1][idx], dp[j][i] + 1);
        }
    }
    return dp[2][N + 1] >= K + 1;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    cin >> N >> L;
    cin >> K;
    a.resize(N + 2);
    a[0] = 0;
    for (int i = 1; i <= N; i++) {
        cin >> a[i];
    }
    a[N + 1] = L;

    int ng = 1;
    int ok = L + 1;
    while (ok - ng > 1) {
        int mid = (ok + ng) / 2;
        if (check(mid)) {
            ng = mid;
        } else {
            ok = mid;
        }
    }
    cout << ng << "\n";

    return 0;
}