#include <fstream>
#include <deque>
using namespace std;

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

int a[5000001], n, k;
deque <int> dq;
void Solve ()
{
    fin >> n >> k;
    for (int i = 1; i <= n; i++)
        fin >> a[i];
    long long sum = 0;
    for (int i = 1; i <= n; i++)
    {
        if (!dq.empty() && dq.front() == i - k)
            dq.pop_front();
        while (!dq.empty() && a[dq.back()] >= a[i])
            dq.pop_back();
        dq.push_back(i);
        if (i >= k) sum += a[dq.front()];
    }
    fout << sum << "\n";
    fout.close();
}

int main()
{
    Solve();
    return 0;
}