#include <bits/stdc++.h>

using namespace std;

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

int v[5000005];
deque<int> dq;

int main()
{
    int  n, k;
    fin >> n >> k;

    for (int i = 1; i <= n; i++)
    {
        fin >> v[i];
    }
    dq.push_back(1);

    long long s = 0;

    for (int i = 2; i <= n; i++)
    {
        while (v[i] <= v[dq.back()] && !dq.empty())
            dq.pop_back();

        dq.push_back(i);

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

        if (i >= k)
            s += v[dq.front()];
    }

    fout << s;

    return 0;
}