#include <bits/stdc++.h>
#define NMAX 5000008

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

int n, k, v[NMAX];
deque <int> D;
long long ans;

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

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

    for (int i = 1; i <= n; i++)
    {
        while (!D.empty() && v[D.back()] > v[i])
            D.pop_back();
        D.push_back(i);

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

        if (i >= k) ans += v[D.front()];
    }

    fout << ans;
    return 0;
}