#include <fstream>

using namespace std;
int v[5000005],n,k,i,deck[5000005],vf,vf1;
long long sol;
ifstream fin("deque.in");
ofstream fout("deque.out");
int main()
{
    fin>>n>>k;
    for (i=1;i<=n;i++)
    fin>>v[i];
    for (i=1;i<=n;i++)
    {
        while(vf1+1!=vf)
        {
            if(deck[vf]+k-1<i) vf++;
            else break;
        }
        while(vf1!=vf-1)
        {
            if(v[deck[vf1]]>=v[i]) vf1--;
            else break;
        }
        deck[++vf1]=i;
        if (i>=k)
        sol+=v[deck[vf]];
  }
  fout<<sol;
}