#include <fstream>
#include <deque>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
struct st
{
    int val, ord;
};
deque <st> coada;
int n, k, x;
long long suma;
int main()
{
    f >> n >> k >> x;
    st el;
    el.val = x;
    el.ord = 1;
    coada.push_back(el);
    for(int i = 2; i <= n; i++)
    {
        f >> x;
        st elo;
        elo.val = x;
        elo.ord = i;
        while(!coada.empty() && x <= coada.back().val)
            coada.pop_back();
        coada.push_back(elo);
        if(i >= k)
        {
            while(i - coada.front().ord + 1 > k)
                coada.pop_front();
            suma += coada.front().val;
        }
    }
    g << suma;
    f.close();
    g.close();
}