#include <fstream>
#include <deque>
using namespace std;
ifstream fin ("deque.in");
ofstream fout ("deque.out");
deque <int> d;
int n,k,v[5000001],i,s;
int main()
{
    fin>>n>>k;
    for (i=1; i<=n; i++)
    {
        fin>>v[i];
    }
    d.push_back(1);
    for (i=2; i<=n; i++)
    {
        while (!d.empty()&&v[d.back()]>=v[i])
        {
            if (d.size()!=0)
            {
                d.pop_back();
            }
            else break;
        }
        d.push_back(i);
        if (d.back()-d.front()>=k) {
                                    d.pop_front();}
        if (i>=k) s=s+v[d.front()];}



        fout<<s;
            return 0;
        }