#include <iostream>
#include <fstream>
#include <deque>

using namespace std;

ifstream fin("deque.in");
ofstream fout("deque.out");

int n, nr, k;
long long sum;
deque < pair < int, int > > coada;

int main()
{
    fin >> n >> k;
    for(int i = 1; i <= n; i++)
    {
        int x;
        fin >> x;
        while(!coada.empty() && coada.back().first >= x)
            coada.pop_back();
        coada.push_back(make_pair(x, i));
        if(coada.front().second == i - k)
            coada.pop_front();
        if(i >= k)
            sum += coada.front().first;
    }
    fout << sum;
}