#include <iostream>
#include <fstream>
#include <deque>
using namespace std;

 long long int v[5000001],coada[5000001];

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

   long long int n,k,index_1=0,index_2=0,suma=0,i;
   f>>n>>k;
   for(i=1;i<=n;i++)
        f>>v[i];

    for(i=1;i<=n;i++)
    {
        while(index_1<=index_2 && v[i]<v[coada[index_2]] )
        {
                index_2--;
        }


        index_2++;
        coada[index_2]=i;

        if(coada[index_1]<=i-k)
            index_1++;

        if(k<=i)
            suma=suma+v[coada[index_1]];
    }


    g<<suma;
    return 0;
}