#include <fstream>
#include <deque>

using namespace std;

ifstream f("deque.in");
ofstream g("deque.out");

int n, k, i, x;
int v[5000001];
long long rez;

deque < int > coada;

int main()
{
    f >> n >> k;

    for (i=1; i<=n; i++)
    {
        f >> v[i];

        while (!coada.empty() && v[i] <= v[coada.back()])
            coada.pop_back();
        coada.push_back(i);

        if (coada.front() == i-k)
            coada.pop_front();

        if (i >= k)
            rez += v[coada.front()];
    }

    g << rez;

    return 0;
}