#include <bits/stdc++.h>
#define int long long

using namespace std;

int v[5000001];

struct q
{
    int indice;
    int val;
};

q coada[5000001];

signed main()
{
    ifstream fin("deque.in");
    ofstream fout("deque.out");
    int n,i,l,r,j,k,s,b;
    fin >> n >> k;
    for (i=1; i<=n; i++)
        fin >> v[i];
    l=1;
    r=1;
    j=0;
    coada[0].val=-10000001;
    s=0;
    for (i=1; i<=n; i++)
    {
        b=j;
        while (coada[b].indice>=i-k+1)
        {
            if (v[i]<=coada[j].val && coada[j].indice>=i-k+1)
            j--;
            b--;
        }
        j++;
        b++;
        coada[j].val=v[i];
        coada[j].indice=i;
        if (i>=k)
        {
            s+=coada[b].val;
        }
    }
    fout << s;
    return 0;
}