#include <fstream>

using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
int v[5000000],d[5000000];
int main()
{
    int st=0,dr=-1,n,k,i,s=0;
    fin>>n>>k;
    for(i=0;i<n;i++){
      fin>>v[i];
    }
    for(i=0;i<n;i++){
      if(st<=dr && d[st]==i-k){
        st++;
      }
      while(st<=dr && v[d[dr]]>=v[i]){
        dr--;
      }
      d[++dr]=i;
      if(i>=k-1)
        s+=v[d[st]];
    }
    fout<<s;
    fin.close();
    fout.close();
    return 0;
}