#include <fstream>
#include <deque>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
deque <int> d;
const int NMAX=5000003;
int v[NMAX];
int n,k;
long long s;
void citire()
{
    fin>>n>>k;
    for(int i=1;i<=n;++i)
        fin>>v[i];
}
int main()
{
    citire();
    for(int i=1;i<=n;++i)
    {
        if(!d.empty() and d.front()==i-k)
            d.pop_front();
        while(!d.empty() and v[d.back()]>=v[i])
            d.pop_back();
        d.push_back(i);
        if(i>=k)
            s+=v[d.front()];
    }
    fout<<s<<' ';

}