#include <fstream>

using namespace std;

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

int n,k,i;
int p=1,q;
int v[5000001],dmin[5000001];
int minim;
long long suma;

int main()
{
    f>>n>>k;
    for (i=1;i<=n;i++)
        f>>v[i];
    for (i=1;i<=n;i++)
    {
        while (p<=q && v[dmin[q]]>=v[i])
            q--;
        q++;
        dmin[q]=i;

        if (i==k+dmin[p])
            p++;

        if (i>=k)
            suma+=v[dmin[p]];
    }
    g<<suma;
    return 0;
}