15678

#include <iostream>
#include <string>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <vector>
#include <set>
#include <map>
#include <stack>
#include <queue>
#include <deque>
#include <unordered_map>
#include <iomanip>
#include <regex>
#include <numeric>
using namespace std;
#define pii pair<long long , long long>
#define FAST ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL)
const long long dx[4] = {0, 1, 0, -1}, dy[4] = {1, 0, -1, 0};
const long long MAX = 100005;

long long n, d;
long long arr[MAX], dp[MAX];
deque<long long> dq;

int main() {
    //freopen("talent.in", "r", stdin);
    //freopen("talent.out", "w", stdout);
    FAST;
    cin >> n >> d;
    for(long long i = 0; i < n; i++){
        cin >> arr[i];
    }
    long long ans = -2e9;
    for(long long i = n - 1; i >= 0; i--){
        dp[i] = arr[i];
        if(!dq.empty()){
            dp[i] = max(dp[i], dp[dq.front()] + arr[i]);
        }
        //cout << i << " " << dp[i] << "\n";
        ans = max(ans, dp[i]);

        if(i >= n - d){
            while(!dq.empty() and dp[i] >= dp[dq.back()]){
                dq.pop_back();
            }
            dq.push_back(i);
        }
        else{
            while(!dq.empty() and dq.front() >= i + d){
                dq.pop_front();
            }
            while(!dq.empty() and dp[i] >= dp[dq.back()]){
                dq.pop_back();
            }
            dq.push_back(i);
        }
    }
    cout << ans << "\n";
}