#include <bits/stdc++.h>

using namespace std;

const int LMAX = 5000007;

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

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

int main()
{
    int n, k;
    long long s = 0;
    fin >> n >> k;

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

    dq.push_back(1);

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