#include <iostream>
#include <fstream>
#include <deque>
using namespace std;
deque <long long> deq;
deque <int> poz;
int main()
{
    int rsp=0,n,k,x;
    ifstream f ("deque.in");
    ofstream g ("deque.out");
    f>>n>>k;
    for (int i=1; i<=n; i++)
    {
        f>>x;
        while (!deq.empty() && x<=deq.back())
        {
            deq.pop_back();
            poz.pop_back();
        }
        deq.push_back(x);
        poz.push_back(i);
        if (!deq.empty() && poz.front()==i-k)
        {
            deq.pop_front();
            poz.pop_front();
        }
        if (i>=k) rsp+=deq.front();
    }
    g<<rsp;
}