#pragma region templates
//C
#ifndef _GLIBCXX_NO_ASSERT
#include <cassert>
#endif
#include <cctype>
#include <cerrno>
#include <cfloat>
#include <ciso646>
#include <climits>
#include <clocale>
#include <cmath>
#include <csetjmp>
#include <csignal>
#include <cstdarg>
#include <cstddef>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>

#if __cplusplus >= 201103L
#include <ccomplex>
#include <cfenv>
#include <cinttypes>
#include <cstdalign>
#include <cstdbool>
#include <cstdint>
#include <ctgmath>
#include <cwchar>
#include <cwctype>
#endif

// C++
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <typeinfo>
#include <utility>
#include <valarray>
#include <vector>

#if __cplusplus >= 201103L
#include <array>
#include <atomic>
#include <chrono>
#include <condition_variable>
#include <forward_list>
#include <future>
#include <initializer_list>
#include <mutex>
#include <random>
#include <ratio>
#include <regex>
#include <scoped_allocator>
#include <system_error>
#include <thread>
#include <tuple>
#include <typeindex>
#include <type_traits>
#include <unordered_map>
#include <unordered_set>
#endif

using i8  = std::int8_t;
using i16 = std::int16_t;
using i32 = std::int32_t;
using i64 = std::int64_t;

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

using f32 = float;
using f64 = double;

using vi32  = std::vector<i32>;
using vu32  = std::vector<u32>;
using vi64  = std::vector<i64>;
using vu64  = std::vector<u64>;

using vvi32 = std::vector<vi32>;
using vvu32 = std::vector<vu32>;
using vvi64 = std::vector<vi64>;
using vvu64 = std::vector<vu64>;

using pi32  = std::pair<i32,i32>;
using pu32  = std::pair<u32,u32>;
using pi64  = std::pair<i64,i64>;
using pu64  = std::pair<u64,u64>;

using vpi32 = std::vector<pi32>;
using vpu32 = std::vector<pu32>;
using vpi64 = std::vector<pi64>;
using vpu64 = std::vector<pu64>;

using si32  = std::stack<i32>;
using si64  = std::stack<i64>;
using su32  = std::stack<u32>;
using su64  = std::stack<u64>;

using qi32  = std::queue<i32>;
using qi64  = std::queue<i64>;
using qu32  = std::queue<u32>;
using qu64  = std::queue<u64>;


#define FOR(i,a,b) for(i64 i=(a),i##_len=(b);i<i##_len;++i)
#define RFOR(i,a,b) for(i64 i=(a),i##_len=(b); i>i##_len; --i)
#define REP(i,n) FOR(i,0,n)
#define RREP(i,n) for(i64 i=static_cast<i64>(n-1); i >= 0; --i)
#define REPS(i,n) for(i64 i=1LL; i<=static_cast<i64>(n); ++i)
#define RREPS(i,n) RFOR(i,n,0)

#define ALL(obj) (obj).begin(),(obj).end()
#define CLR(ar,val) memset(ar, val, sizeof(ar))
#define SZ(obj) (static_cast<i32>(obj.size()))
#define cauto const auto&
#define pb push_back
#define mp make_pair

const i32 dx[4]={1,0,-1,0};
const i32 dy[4]={0,1,0,-1};
const i32 INF32 = 0x3F3F3F3F;
const i64 INF64 = 0x3F3F3F3F3F3F3F3F;

template<class T> inline bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T> inline bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }

class range {
private:
    struct I {
        i32 x;
        i32 operator*() { return x; }
        bool operator!=(I& lhs) { return x<lhs.x; }
        void operator++() { ++x; }
    };
    I i,n;
public:
    explicit range(int n) : i({0}), n({n}) { }
    range(int i,int n) : i({i}), n({n}) { }
    I& begin() { return i; }
    I& end() { return n; }
};

struct IoSetup {
    IoSetup() {
        std::cin.tie(nullptr);
        std::ios::sync_with_stdio(false);
        std::cout << std::fixed << std::setprecision(10);
        std::cerr << std::fixed << std::setprecision(10);
    }
}iosetup;

template<typename A, typename B> std::istream &operator>>(std::istream &is, std::pair<A, B> &p) { is >> p.first >> p.second;return is; }
template<typename A, typename B> std::ostream &operator<<(std::ostream &os, const std::pair<A, B>& p) { os << p.first << ' ' << p.second;return os; }
template<typename T> std::istream &operator>>(std::istream &is, std::vector<T> &v) { for(T& in : v) is >> in; return is; }
template<typename T> std::ostream &operator<<(std::ostream &os, const std::vector<T> &v) { for(i32 i = 0; i < SZ(v); i++) os << v[i] << (i+1 != SZ(v) ? " " : ""); return os; }

#pragma endregion

#pragma region slide-min

template<typename T>
struct SlideMin {
    vi32 deq;
    std::vector<T> res;
    i32 n,k;
    SlideMin(std::vector<T> array, i32 sz){
        n = SZ(array), k = sz;
        deq.resize(n), res.resize(n);
        i32 s = 0, t = 0;
        REP(i,n){
            while (s < t && array[deq[t-1]] <= array[i]) t--;
            deq[t++] = i;
            res[i] = array[deq[s]];
            if (deq[s] == i - k + 1){
                s++;
            }
        }
    }
};

#pragma endregion

i32 main() {
    /* https://atcoder.jp/contests/cf16-tournament-round3-open/tasks/asaporo_d */
    
    using namespace std;

    i32 N, M, K; cin >> N >> M >> K;
    vi64 A(N);
    REP (i, N) cin >> A[i];

    SlideMin<i64> st(A, M);

    REP(i,K-1) {
        vi64 B(N, -(1LL << 60));
        for (i64 j = 1 ; j < N; ++j) {
            chmax(B[j], st.res[j - 1] + (i + 2) * A[j]);
        }
        st = SlideMin<i64>(B, M);
    }

    cout << *max_element(ALL(st.res)) << endl;
    return 0;
}

Measured memory_bytes: 4976