#include <fstream>
using namespace std;

const int MAXN = 5000005;

ifstream in("deque.in");
ofstream out("deque.out");

int n,k;
int Deque[MAXN];
int p,q;
int v[MAXN];
long long rasp = 0;

void citire()
{
    in >> n >> k;
    for (int i = 1;i <= n;++i)
        in >> v[i];
}

void prelucrare()
{
    p = 1;
    q = 0;
    for (int i = 1;i <= n;++i)
    {
        while(p <= q && v[Deque[q]] >= v[i])
            --q;
        Deque[++q] = i;

        while(Deque[p] <= i - k)
            ++p;

        if (i >= k)
            rasp += v[Deque[p]];
    }
}

int main()
{
    citire();
    prelucrare();
    out << rasp << '\n';
    return 0;
}