#include <fstream>
#include <vector>
#include <deque>


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

int main ()
{
  int n,k;
  cin >> n >> k;
  deque<int> dq;
  vector <int> rez(n+1);
  vector<int> v(n+1);
  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);
    while (!dq.empty() && dq.front()<=i-k)
      dq.pop_front();
    rez[i]=v[dq.front()];
  }
  long long s=0;
  for (int i=1;i<=n;++i)
  {
    if (i>=k)
      s+=rez[i];
  }
  cout << s;

}