#include<fstream>
#include<deque>

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

int n,k,i,v[5000001];
long long suma;

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