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

using ll = long long;

constexpr ll INF = (1LL << 62);

template <class F>
int bsearch(int low, int high, F pred) {
    assert(pred(low));

    int lo = low;
    int hi = high;
    int res = low;

    while (lo <= hi) {
        int m = (lo + hi) / 2;

        if (pred(m)) {
            res = max(res, m);
            lo = m + 1;
        } else {
            hi = m - 1;
        }
    }

    return res;
}

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

    int N, L;
    cin >> N >> L;

    int K;
    cin >> K;

    vector<int> A(N);
    for (int i = 0; i < N; i++) {
        cin >> A[i];
    }

    vector<int> cakes;

    int prev = 0;
    for (int a : A) {
        cakes.push_back(a - prev);
        prev = a;
    }
    cakes.push_back(L - prev);

    int sz = (int)cakes.size();

    vector<ll> acc(sz);
    partial_sum(cakes.begin(), cakes.end(), acc.begin());

    auto can = [&](int m) -> bool {
        vector<vector<ll>> dp(sz + 1, vector<ll>(3, -INF));

        dp[0][0] = 0;

        for (int i = 0; i < sz; i++) {
            for (int j = 0; j < 3; j++) {
                dp[i + 1][j] = max(dp[i + 1][j], dp[i][j] + 1);
            }

            ll x = (i > 0 ? acc[i - 1] : 0);

            int p = lower_bound(acc.begin(), acc.end(), x + m) - acc.begin();

            if (p < sz) {
                for (int j = 0; j < 2; j++) {
                    dp[p + 1][j + 1] =
                        max(dp[p + 1][j + 1], dp[i][j] + 1);
                }
            }
        }

        return dp[sz][2] > K;
    };

    int ans = bsearch(1, L, can);

    cout << ans << '\n';

    return 0;
}