#include <fstream>
#include <deque>

using namespace std;

ifstream cin("deque.in");
ofstream cout("deque.out");

int v[5000001];

int main()
{
    int n, k, s = 0;
    cin >> n >> k;
    deque<int> dq;

    for (int i = 1; i <= n; i++)
    {
        cin >> v[i];
    }
    for (int i = 1; i <= n; i++)
    {
        while (!dq.empty() && v[dq.back()] >= v[i])
        {
            dq.pop_back();
        }
        dq.push_back(i);
        if (dq.front() <= i - k)
        {
            dq.pop_front();
        }
        if (i >= k)
        {
            s += v[dq.front()];
        }
    }

    cout << s;
    return 0;
}