#include <fstream>
#include <deque>

#define DIM 5000001

using namespace std;

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

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

int main()
{
    long long n, k;
    fin >> n >> k;
    for (int i = 1; i <= n; i++)
        fin >> v[i];

    dq.push_front(1);
    long long sum = 0;
    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)
            sum += v[dq.front()];
    }
    fout << sum;

    return 0;
}