#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
#define rep(i, n) REP(i, 0, n)
#define REP(i, s, e) for (int i = (s); i < (int)(e); i++)
#define repr(i, n) REPR(i, n, 0)
#define REPR(i, s, e) for (int i = (int)(s - 1); i >= (int)(e); i--)
#define all(r) r.begin(), r.end()
#define rall(r) r.rbegin(), r.rend()

typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vl;

template <typename T, typename U>
T chmax(T& a, const U& b) {
    if (a >= b) return false;
    a = b;
    return true;
}
template <typename T, typename U>
T chmin(T& a, const U& b) {
    if (a <= b) return false;
    a = b;
    return true;
}

void yes_no(bool f, string yes = "Yes", string no = "No") { cout << (f ? yes : no) << "\n"; }

void solve() {
    ll n, l, k;
    cin >> n >> l >> k;
    const int N = n;
    vl a(n);
    rep(i, n) cin >> a[i];
    a.insert(a.begin(), 0);
    a.emplace_back(l);
    // rep(i, a.size()) cout << " " << a[i];
    // cout << '\n';
    auto jd = [&](ll x) -> bool {
        // cout << x << '\n';
        int n = a.size();
        const ll inf = 1e18;
        vl s(n, inf);
        rep(i, n) {
            if (a[n - 1] - a[i] < x) continue;
            ll ok = n - 1, ng = i;
            while (ok - ng > 1) {
                ll m = (ok + ng) / 2;
                if (a[m] - a[i] >= x) ok = m;
                else ng = m;
            }
            s[i] = ok - i;
        }
        // rep(i, n) cout << " " << s[i];
        // cout << '\n';
        vl t(n, inf);
        repr(i, n - 1) t[i] = min(t[i + 1], s[i]);
        rep(i, n) {
            if (i + s[i] < n && N + 1 - (s[i] + t[i + s[i]]) >= k - 1) return true;
        }
        return false;
    };
    ll ok = 0, ng = 1e18;
    while (ng - ok > 1) {
        ll mid = (ok + ng) / 2;
        if (jd(mid)) ok = mid;
        else ng = mid;
    }
    cout << ok << '\n';
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    int t = 1;
    // cin >> t;
    rep(ti, t) solve();
    return 0;
}