#include<bits/stdc++.h>

#define ll long long
#define turbo ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define pii pair<int, int>
#define pll pair<long long, long long>
#define pb push_back
#define f first
#define s second
#define hello cout<<"Hello World";
#define endl "n"
#define mid (l+r)/2

using namespace std;

int n, k;

deque<pll> q;

void dodaj(ll ans, ll index)
{
    while(!q.empty() and q.back().f >= ans)
        q.pop_back();
    q.push_back({ans, index});
    while(!q.empty() and index-q.front().s >= k)
        q.pop_front();
    q.push_back({ans, index});
}

int main()
{
    cin >> n >> k;
    q.push_back({0, -1});
    for(int i = 0; i < n; i++)
    {
        ll x;
        cin >> x;
        dodaj(x+q.front().f,i);
    }
    cout << q.front().f;
}