#include <fstream>

using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
int n,k,v[5000001],dq[5000001],p,u,i;
long long s;
int main()
{  f>>n>>k;

   for(i=1;i<=n;i++)
       f>>v[i];
  p=u=1;
  dq[p]=1;
  for(i=2;i<=n;i++){
     while(p<=u&&v[i]<=v[dq[u]]){
          u--;
          }
      u++;
      dq[u]=i;
      if(i-dq[p]>=k)
          p++;
      if(i>=k)
         s=s+v[dq[p]];
  }
  g<<s;


    return 0;
}