#include<fstream>
using namespace std;
int v[5000005],dq[5000005],n,k; 
int main()
{
  ifstream fin("deque.in");
  ofstream fout("deque.out");
  fin>>n>>k;
  int i;
  for(i=1;i<=n;i++)
    fin>>v[i];
  int st=1,dr=0;
  long long s=0;
  for(i=1;i<=n;i++)
  {
    if(i-dq[st]>=k)
       st++;
    while(v[i]<=v[dq[dr]] && st<=dr)
        dr--;
    dq[++dr]=i;
    if(i>=k)
     s+=v[dq[st]];
    }
  fout<<s;
  return 0;
}