#include <iostream>
#include <fstream>
using namespace std;
ifstream fin ("deque.in");
ofstream fout ("deque.out");
int a[5000001],n,i,d[5000001],p,u,k,s;
int main()
{
   fin>>n>>k;
   for(i=1;i<=n;i++)
        fin>>a[i];
  p=u;
  d[1]=1;
  for(i=1;i<=n;i++){
        while(a[i]<a[d[u]]&&p<=u)
        --u;
        d[++u]=i;
        if(i-d[p]==k)
            p++;
        if(i>=k)
            s+=a[d[p]];
  }
  fout<<s;
    return 0;
}