#include <fstream>
#include <deque>

using namespace std;

ifstream f ("deque.in");
ofstream g ("deque.out");

int n, i, v[5000005], aux, k;
long long suma;
deque < int > coada;

int main()
{
 f >> n >> k;
  for (i=1; i<=n; i++)
     f >> v[i];
  for (i=1; i<=n; i++)
  {
      aux = v[i];
       while (!coada.empty() && v[coada.back()] >= aux)
        coada.pop_back();
     coada.push_back(i);
     if (coada.front() == i-k)
        coada.pop_front();
     if (i >= k && i <= n)
        suma += v[coada.front()];
  }
 g << suma;
    return 0;
}