#include<iostream>
#include<queue>
#include<cstring>

using namespace std;

const int N = 10005;

int n,w,s;
int a[N];
long long d[N],r[N];
deque<int>  q;

int main(){
	cin >> n >> w >> s;

	for (int i=1;i<=n;++i){
		cin >> a[i];
		d[i] = -1e17;
		r[i] = -1e17;
	}
	d[1] = 0;
	for (int i=1;i<=n;++i){
		for (int j=1;j<s;++j){
			while (!q.empty() && d[q.back()]<=d[j]) q.pop_back();
			q.push_back(j);
		}
		int p = min(w,i);
		for (int j=1;j<=p;++j){
			if (!q.empty() && j-1>q.front()) q.pop_front();
			int k = j+s-1;
			if (k<=w) {
				while (!q.empty() && d[q.back()]<=d[k]) q.pop_back();
				q.push_back(k);
			}
			r[j] = d[q.front()]+j*a[i];
		}
		while (!q.empty()) q.pop_back();
		memcpy(d,r,sizeof(r));
	}
	long long  ans = -1e17;
	for (int i=1;i<=w;++i)
		ans = max(ans,d[i]);
	cout << ans << endl;
}