#include <fstream>
#include <deque>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
deque<int>H;
int v[5000001];
int main()
{
    int n,k,i,tot=0;
    fin>>n>>k;
    for(i=1;i<=n;i++)
    {
        fin>>v[i];
        while(!H.empty())
        {
            if(H.front()+k-1<i) H.pop_front();
            else break;
        }
        while(!H.empty())
        {
            if(v[H.back()]>=v[i]) H.pop_back();
            else break;
        }
        H.push_back(i);
        if(i>=k) tot+=v[H.front()];
    }
    fout<<tot;
}