#include <fstream>
#include <deque>
using namespace std;

ifstream f("deque.in");
ofstream g("deque.out");
int n,v[5000005],k;
long long sum;
deque <int> dq;
int main()
{
    f >> n >> k;
     for ( int i = 1 ; i <= n ; i ++ )
      f >> v[i];
      for ( int i = 1 ; i <= n ; i ++ )
      {
           while(!dq.empty()&&v[i]<=v[dq.back()])
             dq.pop_back();
            dq.push_back(i);
            if(dq.front()==i-k)
              dq.pop_front();
            if ( i >= k )
            sum+=v[dq.front()];
      }
   g << sum;
    return 0;
}