#include <fstream>
#include <deque>

using namespace std;

const int NMAX = 5000000;

int v[1 + NMAX];

deque<int> dq;

int main()
{
    ifstream in("deque.in");
    ofstream out("deque.out");

    int n, k;
    in >> n >> k;

    long long sol = 0;

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

        while (!dq.empty() && v[dq.front()] >= v[i])
            dq.pop_front();

        dq.push_front(i);

        while (!dq.empty() && i - dq.back() + 1 > k)
            dq.pop_back();

        if (!dq.empty() && i >= k)
            sol += v[dq.back()];
    }

    out << sol << '\n';

    in.close();
    out.close();

    return 0;
}