#include <fstream>
#include <deque>
using namespace std;
ifstream fin ("deque.in");
ofstream fout ("deque.out");
int v[5000001],n,k,i,j,o,s,p,u;
deque <int> d;
int main()
{
   fin >> n >>k;
   for(i=1;i<=n;i++)
   {
       fin >> v[i];
   }

   for(i=1;i<=n;i++)
   {
       while(!d.empty()&&v[i]<v[d[d.size()-1]])
            d.pop_back();
       d.push_back(i);
       if(d[0]==i-k)
        d.pop_front();
       if(i>=k)
        s=s+v[d[0]];
   }

    fout<<s;

}