#include <fstream>

using namespace std;
int n,k,i,COADA[5000002],a[5000002],u,sum;
ifstream f ("deque.in");
ofstream g ("deque.out");
void formcoada( int COADA[5000002], int a[5000002], int c, int v)
{
    int s=1,d=0;
    int sum=0;
    for (int i=0; i<c; i++)
    {
        f>>a[i];
        if (s<=d && COADA[s]==i-v)
        {
            s++;
        }
        while (a[i]<=a[COADA[d]] && d>=s)
        {
            d--;
        }
        d++;
        COADA[d]=i;
        if (i>=v-1)
        {
            sum=sum+a[COADA[s]];
        }
    }
    g<<sum<<'\n';
}
int main()
{
    f>>n>>k;
    formcoada(COADA,a,n,k);
    return 0;
}