//
//  main.cpp
//  deque
//
//  Created by Mara Dascalu on 15/03/2021.
//

#include <iostream>
#include <fstream>

using namespace std;

ifstream input("deque.in");
ofstream output("deque.out");

int n, k, sum = 0, st, dr, v[5000001], deq[5000001];


int main()
{
    input>>n>>k;
    st = 1;
    dr = 0;
    for (int i = 1; i <=n; i++)
    {
        input>>v[i];
        while (st <= dr && v[i] <= v[deq[dr]])
            dr--;
        deq[++dr] = i;
        if (i - k == deq[st]) st++;
        if(i >= k) sum += v[deq[st]];
    }
    output<<sum;
}