#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
#define pb push_back
#define all(a) a.begin(), a.end()
#define sz(a) ((int)a.size())
#ifdef Doludu
template <typename T>
ostream& operator << (ostream &o, vector <T> vec) {
    o << "{"; int f = 0;
    for (T i : vec) o << (f++ ? " " : "") << i;
    return o << "}";
}
void bug__(int c, auto ...a) {
    cerr << "\e[1;" << c << "m";
    (..., (cerr << a << " "));
    cerr << "\e[0m" << endl;
}
#define bug_(c, x...) bug__(c, __LINE__, "[" + string(#x) + "]", x)
#define bug(x...) bug_(32, x)
#define bugv(x...) bug_(36, vector(x))
#define safe bug_(33, "safe")
#else
#define bug(x...) void(0)
#define bugv(x...) void(0)
#define safe void(0)
#endif
const int mod = 998244353, N = 2000006;

int main() {
    ios::sync_with_stdio(false), cin.tie(0);
    int n, l, k;
    cin >> n >> l >> k;
    vector <int> a = {0};
    for (int i = 0, x; i < n; ++i) {
        cin >> x;
        a.pb(x);
    }
    a.pb(l);
    auto ask = [&](int x) {
        vector dp(sz(a), vector(3, -1 << 30));
        dp[0][0] = 0;
        for (int i = 0, pos = 0; i + 1 < sz(a); ++i) {
            for (int j = 0; j <= 2; ++j) {
                dp[i + 1][j] = max(dp[i + 1][j], dp[i][j] + 1);
            }
            while (pos < sz(a) && a[pos] < a[i] + x) pos++;
            if (pos < sz(a)) {
                for (int j = 0; j < 2; ++j) {
                    dp[pos][j + 1] = max(dp[pos][j + 1], dp[i][j] + 1);
                }
            }
        }
        int ans = dp[sz(a) - 1][2];
        bug(x, ans);
        return ans >= k + 1;
    };
    int L = 0, R = l + 1;
    while (R - L > 1) {
        int m = L + R >> 1;
        if (ask(m)) L = m;
        else R = m;
    }
    cout << L << "\n";
}