#include <fstream>

using namespace std;
ifstream cin("deque.in");
ofstream cout("deque.out");
struct element
{
    int val, poz;
};
element v[5000005];
int main()
{
    int n, k;
    cin>>n>>k;
    element a;
    int st=1, dr=1;
    cin>>a.val;
    a.poz=1;
    v[1]=a;
    int s=0;
    for (int i=2; i<=n; i++)
    {
        cin>>a.val;
        a.poz=i;
        while (a.val<=v[dr].val && dr)
            dr--;
        dr++;
        v[dr]=a;
        if (i>=k)
        {
            if (v[st].poz<=i-k)
                st++;
            s+=v[st].val;
        }
    }
    cout<<s;
    return 0;
}