#include <iostream>
#include <iomanip>
#include <cassert>
#include <vector>
#include <algorithm>
#include <utility>
#include <numeric>
#include <tuple>
#include <ranges>
#include <random>
// #include "Src/Number/IntegerDivision.hpp"


#include <cstdint>
#include <cstddef>

namespace zawa {

using i16 = std::int16_t;
using i32 = std::int32_t;
using i64 = std::int64_t;
using i128 = __int128_t;

using u8 = std::uint8_t;
using u16 = std::uint16_t;
using u32 = std::uint32_t;
using u64 = std::uint64_t;

using usize = std::size_t;

} // namespace zawa

#include <cmath>
#include <functional>
#include <type_traits>

namespace zawa {

namespace internal {

template <class T>
T MidPoint(T a, T b) {
    if (a > b) std::swap(a, b);
    return a + ((b - a) >> 1);
}

template <class T>
T Abs(T a, T b) {
    return (a >= b ? a - b : b - a);
}

} // namespace zawa::internal

template <class T, class Function>
T BinarySearch(T ok, T ng, const Function& f) {
    static_assert(std::is_integral_v<T>, "T must be integral type");
    static_assert(std::is_convertible_v<Function, std::function<bool(T)>>, "f must be function bool(T)");
    while (internal::Abs(ok, ng) > 1) {
        T mid{ internal::MidPoint(ok, ng) };
        (f(mid) ? ok : ng) = mid;
    }
    return ok;
}

template <class T, class Function>
T BinarySearch(T ok, T ng, const Function& f, u32 upperLimit) {
    static_assert(std::is_signed_v<T>, "T must be signed arithmetic type");
    static_assert(std::is_convertible_v<Function, std::function<bool(T)>>, "f must be function bool(T)");
    for (u32 _{} ; _ < upperLimit ; _++) {
        T mid{ (ok + ng) / (T)2 };
        (f(mid) ? ok : ng) = mid;
    }
    return ok;
}

} // namespace zawa
// #include "Src/Sequence/CompressedSequence.hpp"
// #include "Src/Sequence/RunLengthEncoding.hpp"
// #include "Src/Algebra/Group/AdditiveGroup.hpp"
// #include "Src/DataStructure/FenwickTree/FenwickTree.hpp"
// #include "Src/DataStructure/SegmentTree/SegmentTree.hpp"
// #include "Src/DataStructure/DisjointSetUnion/DisjointSetUnion.hpp"
// #include "Src/DataStructure/Heap/BinaryHeap.hpp"
namespace zawa {}
using namespace zawa;
// #include "atcoder/modint"
// using mint = atcoder::modint998244353;
// #include <array>
// #include <bit>
// #include <bitset>
// #include <climits>
// #include <cmath>
// #include <set>
// #include <unordered_set>
// #include <map>
// #include <unordered_map>
// #include <optional>
// #include <queue>
// #include <stack>
// #include <deque>
// #pragma GCC target("avx2")
// #pragma GCC optimize("O3")
// #pragma GCC optimize("unroll-loops")
using namespace std;
template <class T, class U>
ostream& operator<<(ostream& os, const pair<T, U>& p) {
    os << '(' << p.first << ',' << p.second << ')';
    return os;
}
template <class T>
ostream& operator<<(ostream& os, const vector<T>& v) {
    for (int i = 0 ; i < ssize(v) ; i++)
        os << v[i] << (i + 1 == ssize(v) ? "" : " ");
    return os;
}
/*
 * bobは1番大きいピースを選ぶ
 * Aliceは2番目に大きいピースを最大化せよ
 * xを二個以上作れるかで二分探索？
 * distinctにx以上の幅を二つ取りたい。それはできそう
 * K個の切れ目を選ぶ必要があるhh。むずいな。
 * dp[i][j] := ith/x以上の切れ目をj個作った -> 無駄にした切れ目の個数の最小値
 * 隣り合ったピースを選んだときがやばそう
 * dp[i][j] := ith/x以上の切れ目をj個作った -> ここまで作ったピースの最大値 
 * これだ。
 */
int main() {
    cin.tie(0);
    cout.tie(0);
    ios::sync_with_stdio(0);
    cout << fixed << setprecision(20);
#if !defined DEBUG
    int N,L,K;
    cin >> N >> L >> K;
    vector<int> A(N);
    for (auto& x : A)
        cin >> x;
    A.insert(A.begin(),0);
    A.push_back(L);
    auto f = [&](int len) -> bool {
        vector<int> to(ssize(A));
        for (int i = 0 ; i < ssize(A) ; i++)
            to[i] = ranges::lower_bound(A,A[i]+len)-A.begin();
        vector dp(ssize(A),vector<int>(3,-1));
        dp[0][0] = 0;
        for (int i = 0 ; i + 1 < ssize(A) ; i++)
            for (int j = 0 ; j <= 2 ; j++)
                if (dp[i][j] != -1) {
                    dp[i+1][j] = max(dp[i+1][j],dp[i][j]+1);
                    if (j + 1 <= 2 and to[i] < ssize(A))
                        dp[to[i]][j+1] = max(dp[to[i]][j+1],dp[i][j]+1);
                }
        return dp[ssize(A)-1][2] >= K+1;
    };
    cout << BinarySearch(1,L+1,f) << '\n';
#else
    mt19937_64 mt{random_device{}()};
    for (int testcase = 0 ; ; ) {
        cerr << "----------" << ++testcase << "----------" << endl;
        
        auto a = solve(), b = naive();
        if (a != b) {
            // print testcase

            cerr << "you: " << a << endl;
            cout << "correct: " << b << endl;
            exit(0);
        }
    }
#endif
}