#include <fstream>
#include <deque>

using namespace std;
deque<int> deck;
int v[5000005],n,k,i;
long long sol;
ifstream fin("deque.in");
ofstream fout("deque.out");
int main()
{
    fin>>n>>k;
    for (i=1;i<=n;i++)
    fin>>v[i];
    for (i=1;i<=n;i++)
    {
        while(!deck.empty())
        {
            if(deck.front()+k-1<i) deck.pop_front();
            else break;
        }
        while(!deck.empty())
        {
            if(v[deck.back()]>=v[i]) deck.pop_back();
            else break;
        }
        deck.push_back(i);
        if (i>=k)
        sol+=v[deck.front()];
  }
  fout<<sol;
}