#ifndef HIDDEN_IN_VS // 折りたたみ用

// 警告の抑制
#define _CRT_SECURE_NO_WARNINGS

// ライブラリの読み込み
#include <bits/stdc++.h>
using namespace std;

// 型名の短縮
using ll = long long; // -2^63 ～ 2^63 = 9 * 10^18（int は -2^31 ～ 2^31 = 2 * 10^9）
using pii = pair<int, int>;	using pll = pair<ll, ll>;	using pil = pair<int, ll>;	using pli = pair<ll, int>;
using vi = vector<int>;		using vvi = vector<vi>;		using vvvi = vector<vvi>;
using vl = vector<ll>;		using vvl = vector<vl>;		using vvvl = vector<vvl>;
using vb = vector<bool>;	using vvb = vector<vb>;		using vvvb = vector<vvb>;
using vc = vector<char>;	using vvc = vector<vc>;		using vvvc = vector<vvc>;
using vd = vector<double>;	using vvd = vector<vd>;		using vvvd = vector<vvd>;
template <class T> using priority_queue_rev = priority_queue<T, vector<T>, greater<T>>;
using Graph = vvi;

// 定数の定義
const double PI = acos(-1);
const vi dx4 = { 1, 0, -1, 0 }; // 4 近傍（下，右，上，左）
const vi dy4 = { 0, 1, 0, -1 };
const vi dx8 = { 1, 1, 0, -1, -1, -1, 0, 1 }; // 8 近傍
const vi dy8 = { 0, 1, 1, 1, 0, -1, -1, -1 };
const int INF = 1001001001; const ll INFL = 4004004004004004004LL;
const double EPS = 1e-12; // 許容誤差に応じて調整

// 入出力高速化
struct fast_io { fast_io() { cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(15); } } fastIOtmp;

// 汎用マクロの定義
#define all(a) (a).begin(), (a).end()
#define sz(x) ((int)(x).size())
#define distance (int)distance
#define Yes(b) {cout << ((b) ? "Yes\n" : "No\n");}
#define YES(b) {cout << ((b) ? "YES\n" : "NO\n");}
#define rep(i, n) for(int i = 0, i##_len = int(n); i < i##_len; ++i) // 0 から n-1 まで昇順
#define repi(i, s, t) for(int i = int(s), i##_end = int(t); i <= i##_end; ++i) // s から t まで昇順
#define repir(i, s, t) for(int i = int(s), i##_end = int(t); i >= i##_end; --i) // s から t まで降順
#define repe(v, a) for(const auto& v : (a)) // a の全要素（変更不可能）
#define repea(v, a) for(auto& v : (a)) // a の全要素（変更可能）
#define repb(set, d) for(int set = 0; set < (1 << int(d)); ++set) // d ビット全探索（昇順）
#define repp(a) sort(all(a)); for(bool a##_perm = true; a##_perm; a##_perm = next_permutation(all(a))) // a の順列全て（昇順）
#define smod(n, m) ((((n) % (m)) + (m)) % (m)) // 非負mod
#define uniq(a) {sort(all(a)); (a).erase(unique(all(a)), (a).end());} // 重複除去
#define EXIT(a) {cout << (a) << endl; exit(0);} // 強制終了

// 汎用関数の定義
template <class T> inline ll pow(T n, int k) { ll v = 1; rep(i, k) v *= n; return v; }
template <class T> inline bool chmax(T& M, const T& x) { if (M < x) { M = x; return true; } return false; } // 最大値を更新（更新されたら true を返す）
template <class T> inline bool chmin(T& m, const T& x) { if (m > x) { m = x; return true; } return false; } // 最小値を更新（更新されたら true を返す）

// 演算子オーバーロード
template <class T, class U> inline istream& operator>>(istream& is, pair<T, U>& p) { is >> p.first >> p.second; return is; }
template <class T> inline istream& operator>>(istream& is, vector<T>& v) { repea(x, v) is >> x; return is; }
template <class T> inline vector<T>& operator--(vector<T>& v) { repea(x, v) --x; return v; }
template <class T> inline vector<T>& operator++(vector<T>& v) { repea(x, v) ++x; return v; }

// 手元環境（Visual Studio）
#ifdef _MSC_VER
#include "local.hpp"
// 提出用（gcc）
#else
#define popcount (int)__builtin_popcount
#define popcountll (int)__builtin_popcountll
#define lsb __builtin_ctz
#define lsbll __builtin_ctzll
#define msb(n) (31 - __builtin_clz(n))
#define msbll(n) (63 - __builtin_clzll(n))
#define gcd __gcd
#define dump(...)
#define dumpel(v)
#define input_from_file(f)
#define output_to_file(f)
#endif

#endif // 折りたたみ用


//--------------AtCoder 専用--------------
#include <atcoder/all>
using namespace atcoder;

using mint = modint1000000007;
//using mint = modint998244353;
//using mint = modint; // mint::set_mod(m);

istream& operator>>(istream& is, mint& x) { ll x_; is >> x_; x = x_; return is; }
ostream& operator<<(ostream& os, const mint& x) { os << x.val(); return os; }
using vm = vector<mint>; using vvm = vector<vm>; using vvvm = vector<vvm>;
//----------------------------------------


void naive() {
	int n, m, l;
	cin >> n >> m >> l;

	vl a(n);
	cin >> a;
	dump(a);

	vl c(l);
	rep(i, n * m) c[i % l] += a[i % n];
	dump(c);

	cout << *max_element(all(c)) << endl;
}


void zikken(ll n, ll m, ll l) {
	vvi c(l);
	rep(i, n * m) c[i % l].push_back(i % n);
	dumpel(c);
}
/*
(n, m, l) = (18, 29, 24) -> g = 6
0: [0 6 12] 0 6 12 0 6 12 0 6 12 0 6 12 0 6 12 0 6 12 0 *
1: [1 7 13] 1 7 13 1 7 13 1 7 13 1 7 13 1 7 13 1 7 13 1 *
2: [2 8 14] 2 8 14 2 8 14 2 8 14 2 8 14 2 8 14 2 8 14 2 *
3: [3 9 15] 3 9 15 3 9 15 3 9 15 3 9 15 3 9 15 3 9 15 3 *
4: [4 10 16] 4 10 16 4 10 16 4 10 16 4 10 16 4 10 16 4 10 16 4 *
5: [5 11 17] 5 11 17 5 11 17 5 11 17 5 11 17 5 11 17 5 11 17 5 *
6: 6 12 0 6 12 0 6 12 0 6 12 0 6 12 0 6 12 0 6 12 0 6 *
7: 7 13 1 7 13 1 7 13 1 7 13 1 7 13 1 7 13 1 7 13 1 7 *
8: 8 14 2 8 14 2 8 14 2 8 14 2 8 14 2 8 14 2 8 14 2 8 *
9: 9 15 3 9 15 3 9 15 3 9 15 3 9 15 3 9 15 3 9 15 3 9 *
10: 10 16 4 10 16 4 10 16 4 10 16 4 10 16 4 10 16 4 10 16 4 10 *
11: 11 17 5 11 17 5 11 17 5 11 17 5 11 17 5 11 17 5 11 17 5 11 *
12: 12 0 6 12 0 6 12 0 6 12 0 6 12 0 6 12 0 6 12 0 6 12 *
13: 13 1 7 13 1 7 13 1 7 13 1 7 13 1 7 13 1 7 13 1 7 13 *
14: 14 2 8 14 2 8 14 2 8 14 2 8 14 2 8 14 2 8 14 2 8 14 *
15: 15 3 9 15 3 9 15 3 9 15 3 9 15 3 9 15 3 9 15 3 9 15 *
16: 16 4 10 16 4 10 16 4 10 16 4 10 16 4 10 16 4 10 16 4 10 16 *
17: 17 5 11 17 5 11 17 5 11 17 5 11 17 5 11 17 5 11 17 5 11 17 *
18: [0 6 12] 0 6 12 0 6 12 0 6 12 0 6 12 0 6 12 0 6 12
19: [1 7 13] 1 7 13 1 7 13 1 7 13 1 7 13 1 7 13 1 7 13
20: [2 8 14] 2 8 14 2 8 14 2 8 14 2 8 14 2 8 14 2 8 14
21: [3 9 15] 3 9 15 3 9 15 3 9 15 3 9 15 3 9 15 3 9 15
22: [4 10 16] 4 10 16 4 10 16 4 10 16 4 10 16 4 10 16 4 10 16
23: [5 11 17] 5 11 17 5 11 17 5 11 17 5 11 17 5 11 17 5 11 17

(n, m, l) = (15, 29, 24) -> g = 3
0: [0 9 3 12 6] 0 9 3 12 6 0 9 3 12 6 0 9 3 12 *
1: [1 10 4 13 7] 1 10 4 13 7 1 10 4 13 7 1 10 4 13 *
2: [2 11 5 14 8] 2 11 5 14 8 2 11 5 14 8 2 11 5 14 *
3: 3 12 6 0 9 3 12 6 0 9 3 12 6 0 9 3 12 6
4: 4 13 7 1 10 4 13 7 1 10 4 13 7 1 10 4 13 7
5: 5 14 8 2 11 5 14 8 2 11 5 14 8 2 11 5 14 8
6: 6 0 9 3 12 6 0 9 3 12 6 0 9 3 12 6 0 9
7: 7 1 10 4 13 7 1 10 4 13 7 1 10 4 13 7 1 10
8: 8 2 11 5 14 8 2 11 5 14 8 2 11 5 14 8 2 11
9: 9 3 12 6 0 9 3 12 6 0 9 3 12 6 0 9 3 12
10: 10 4 13 7 1 10 4 13 7 1 10 4 13 7 1 10 4 13
11: 11 5 14 8 2 11 5 14 8 2 11 5 14 8 2 11 5 14
12: 12 6 0 9 3 12 6 0 9 3 12 6 0 9 3 12 6 0
13: 13 7 1 10 4 13 7 1 10 4 13 7 1 10 4 13 7 1
14: 14 8 2 11 5 14 8 2 11 5 14 8 2 11 5 14 8 2
15: [0 9 3 12 6] 0 9 3 12 6 0 9 3 12 6 0 9 3
16: [1 10 4 13 7] 1 10 4 13 7 1 10 4 13 7 1 10 4
17: [2 11 5 14 8] 2 11 5 14 8 2 11 5 14 8 2 11 5
18: 3 12 6 0 9 3 12 6 0 9 3 12 6 0 9 3 12 6
19: 4 13 7 1 10 4 13 7 1 10 4 13 7 1 10 4 13 7
20: 5 14 8 2 11 5 14 8 2 11 5 14 8 2 11 5 14 8
21: 6 0 9 3 12 6 0 9 3 12 6 0 9 3 12 6 0 9
22: 7 1 10 4 13 7 1 10 4 13 7 1 10 4 13 7 1 10
23: 8 2 11 5 14 8 2 11 5 14 8 2 11 5 14 8 2 11
*/


int main() {
//	input_from_file("input.txt");
//	output_to_file("output.txt");

	ll n, m, l;
	cin >> n >> m >> l;

//	zikken(n, m, l);

	vl a(n);
//	iota(all(a), 0);
	cin >> a;

	ll bh = gcd(n, l);
	ll bw = n / bh;
	dump(bh, bw);
	
	vvl b(bh, vl(bw));
	rep(i, bh) rep(j, bw) b[i][j] = a[(i + j * l) % n];
	dumpel(b);

	vvl b_acc(bh, vl(bw * 2 + 2));
	rep(i, bh) rep(j, bw * 2 + 1) b_acc[i][j + 1] = b_acc[i][j] + b[i][j % bw];
	dumpel(b_acc);

	ll w = n * m / l;
	ll rmd = n * m % l;
	dump(w, rmd);

	vi p(bw);
	rep(j, bw) p[(j * l) % n / bh] = j;
	dump(p);

	ll res = -INFL;

	for (ll i = 0; i < min(n, l); i++) {
		ll x = i % bh;
		ll y = p[(i / bh) % bw];

		ll v = b_acc[x][bw] * (w / bw);
		v += b_acc[x][y + w % bw] - b_acc[x][y];
		if (i < rmd) v += a[(w * l + i) % n];

		chmax(res, v);
	}

	for (ll i = l - 1; i >= max(l - n, 0LL); i--) {
		ll x = i % bh;
		ll y = p[(i / bh) % bw];

		ll v = b_acc[x][bw] * (w / bw);
		v += b_acc[x][y + w % bw] - b_acc[x][y];
		if (i < rmd) v += a[(w * l + i) % n];

		chmax(res, v);
	}

	cout << res << endl;
}