/* #region Head */

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

using ll = long long;
using ull = unsigned long long;
using ld = long double;
using pll = pair<ll, ll>;
template <class T> using vc = vector<T>;
template <class T> using vvc = vc<vc<T>>;
using vll = vc<ll>;
using vvll = vvc<ll>;
using vld = vc<ld>;
using vvld = vvc<ld>;
using vs = vc<string>;
using vvs = vvc<string>;
template <class T, class U> using um = unordered_map<T, U>;
template <class T> using pq = priority_queue<T>;
template <class T> using pqa = priority_queue<T, vc<T>, greater<T>>;
template <class T> using us = unordered_set<T>;

#define REP(i, m, n) for (ll i = (m), i##_len = (ll)(n); i < i##_len; ++(i))
#define REPM(i, m, n) for (ll i = (m), i##_max = (ll)(n); i <= i##_max; ++(i))
#define REPR(i, m, n) for (ll i = (m), i##_min = (ll)(n); i >= i##_min; --(i))
#define REPD(i, m, n, d) for (ll i = (m), i##_len = (ll)(n); i < i##_len; i += (d))
#define REPMD(i, m, n, d) for (ll i = (m), i##_max = (ll)(n); i <= i##_max; i += (d))
#define REPI(itr, ds) for (auto itr = ds.begin(); itr != ds.end(); itr++)
#define ALL(x) begin(x), end(x)
#define SIZE(x) ((ll)(x).size())
#define PERM(c)                                                                                                        \
    sort(ALL(c));                                                                                                      \
    for (bool c##p = 1; c##p; c##p = next_permutation(ALL(c)))
#define UNIQ(v) v.erase(unique(ALL(v)), v.end());

#define endl '\n'
#define sqrt sqrtl
#define floor floorl
#define log2 log2l

constexpr ll INF = 1'010'000'000'000'000'017LL;
constexpr ll MOD = 1'000'000'007LL; // 1e9 + 7
constexpr ld EPS = 1e-12;
constexpr ld PI = 3.14159265358979323846;

template <typename T> istream &operator>>(istream &is, vc<T> &vec) { // vector 入力
    for (T &x : vec) is >> x;
    return is;
}
template <typename T> ostream &operator<<(ostream &os, vc<T> &vec) { // vector 出力 (for dump)
    os << "{";
    REP(i, 0, SIZE(vec)) os << vec[i] << (i == i_len - 1 ? "" : ", ");
    os << "}";
    return os;
}
template <typename T> ostream &operator>>(ostream &os, vc<T> &vec) { // vector 出力 (inline)
    REP(i, 0, SIZE(vec)) os << vec[i] << (i == i_len - 1 ? "\n" : " ");
    return os;
}

template <typename T, typename U> istream &operator>>(istream &is, pair<T, U> &pair_var) { // pair 入力
    is >> pair_var.first >> pair_var.second;
    return is;
}
template <typename T, typename U> ostream &operator<<(ostream &os, pair<T, U> &pair_var) { // pair 出力
    os << "(" << pair_var.first << ", " << pair_var.second << ")";
    return os;
}

// map, um, set, us 出力
template <class T> ostream &out_iter(ostream &os, T &map_var) {
    os << "{";
    REPI(itr, map_var) {
        os << *itr;
        auto itrcp = itr;
        if (++itrcp != map_var.end()) os << ", ";
    }
    return os << "}";
}
template <typename T, typename U> ostream &operator<<(ostream &os, map<T, U> &map_var) { return out_iter(os, map_var); }
template <typename T, typename U> ostream &operator<<(ostream &os, um<T, U> &map_var) {
    os << "{";
    REPI(itr, map_var) {
        auto [key, value] = *itr;
        os << "(" << key << ", " << value << ")";
        auto itrcp = itr;
        if (++itrcp != map_var.end()) os << ", ";
    }
    os << "}";
    return os;
}
template <typename T> ostream &operator<<(ostream &os, set<T> &set_var) { return out_iter(os, set_var); }
template <typename T> ostream &operator<<(ostream &os, us<T> &set_var) { return out_iter(os, set_var); }
template <typename T> ostream &operator<<(ostream &os, pq<T> &pq_var) {
    pq<T> pq_cp(pq_var);
    os << "{";
    if (!pq_cp.empty()) {
        os << pq_cp.top(), pq_cp.pop();
        while (!pq_cp.empty()) os << ", " << pq_cp.top(), pq_cp.pop();
    }
    return os << "}";
}

// dump
#define DUMPOUT cerr
void dump_func() { DUMPOUT << endl; }
template <class Head, class... Tail> void dump_func(Head &&head, Tail &&... tail) {
    DUMPOUT << head;
    if (sizeof...(Tail) > 0) DUMPOUT << ", ";
    dump_func(move(tail)...);
}

// chmax (更新「される」かもしれない値が前)
template <typename T, typename U, typename Comp = less<>> bool chmax(T &xmax, const U &x, Comp comp = {}) {
    if (comp(xmax, x)) {
        xmax = x;
        return true;
    }
    return false;
}

// chmin (更新「される」かもしれない値が前)
template <typename T, typename U, typename Comp = less<>> bool chmin(T &xmin, const U &x, Comp comp = {}) {
    if (comp(x, xmin)) {
        xmin = x;
        return true;
    }
    return false;
}

// ローカル用
#define DEBUG_

#ifdef DEBUG_
#define DEB
#define dump(...)                                                                                                      \
    DUMPOUT << "  " << string(#__VA_ARGS__) << ": "                                                                    \
            << "[" << to_string(__LINE__) << ":" << __FUNCTION__ << "]" << endl                                        \
            << "    ",                                                                                                 \
        dump_func(__VA_ARGS__)
#else
#define DEB if (false)
#define dump(...)
#endif

struct AtCoderInitialize {
    static constexpr int IOS_PREC = 15;
    static constexpr bool AUTOFLUSH = false;
    AtCoderInitialize() {
        ios_base::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr);
        cout << fixed << setprecision(IOS_PREC);
        if (AUTOFLUSH) cout << unitbuf;
    }
} ATCODER_INITIALIZE;

void Yn(bool p) { cout << (p ? "Yes" : "No") << endl; }
void YN(bool p) { cout << (p ? "YES" : "NO") << endl; }

/* #endregion */

/* #region SWAG */

template <typename T> struct SWAG {
    using F = function<T(T, T)>;

  private:
    class Node {
      public:
        T val, sum;
        Node(const T &val, const T &sum) : val(val), sum(sum) {}
    };

    F f;
    stack<Node> front_stack, back_stack;

  public:
    SWAG(const F &f) : f(f), front_stack(), back_stack() {}

    bool empty() const { return front_stack.empty() && back_stack.empty(); }

    size_t size() const { return front_stack.size() + back_stack.size(); }

    T fold_all() const {
        assert(!empty());
        if (front_stack.empty()) {
            return back_stack.top().sum;
        } else if (back_stack.empty()) {
            return front_stack.top().sum;
        } else {
            return f(front_stack.top().sum, back_stack.top().sum);
        }
    }

    void push(const T &x) {
        if (back_stack.empty()) {
            back_stack.emplace(x, x);
        } else {
            T s{f(back_stack.top().sum, x)};
            back_stack.emplace(x, s);
        }
    }

    void pop() {
        assert(!empty());
        if (front_stack.empty()) {
            front_stack.emplace(back_stack.top().val, back_stack.top().val);
            back_stack.pop();
            while (!back_stack.empty()) {
                T s{f(back_stack.top().val, front_stack.top().sum)};
                front_stack.emplace(back_stack.top().val, s);
                back_stack.pop();
            }
        }
        front_stack.pop();
    }
};

template <typename T> struct SWAGVec {
    using F = function<T(T, T)>;

    SWAG<T> swag;
    vc<T> v;
    size_t l, r;

    SWAGVec(const F &f, vc<T> &v) : swag(f), v(v), l(0), r(0) {}

    T fold(size_t i, size_t j) {
        assert(j >= r);
        assert(i >= l);
        while (r < j) swag.push(v[r++]);
        while (l < i) swag.pop(), ++l;
        return swag.fold_all();
    }
};

/* #endregion */

// Problem
void solve() {
    ll n, m, k;
    cin >> n >> m >> k;
    vll a(n);
    cin >> a;

    // 愚直
    // dp[i][j] = i 番目まで見て，i 番目でちょうど j 個目を使ったときの得点最大値
    // vvll dp(n + 1, vll(k + 1, 0));
    // REPM(i, 1, n) REPM(j, 1, i) {
    //     dp[i][j] = j*a[i-1] + max(dp[i-m][j-1], ..., dp[i-1][j-1])
    // }

    auto f = [](ll a, ll b) -> ll { return max(a, b); };
    vll dp(n + 1, 0);
    REPM(j, 1, k) {
        SWAGVec<ll> sv(f, dp);
        dp[j - 1] = 0;
        REPM(i, j, n) dp[i] = j * a[i - 1] + sv.fold(max(0LL, i - m), i);
    }
    cout << *max_element(dp.begin() + k, dp.end()) << endl;
}

// entry point
int main() {
    solve();
    return 0;
}


Measured memory_bytes: 7236