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

ifstream f("deque.in");
ofstream g("deque.out");
deque <int> dq;
int a[5000010],i,sum,k,n;
int main()
{
    f >> n >> k;
     for ( int i = 1 ; i <= n ; i ++ )
        f >> a[i];
     for ( i = 1 ; i <= n ; i ++ )
       {
           while(dq.size() && a[i] <= a[dq.back()])
              dq.pop_back();
            dq.push_back(i);
            if (dq.front()==i-k)
            dq.pop_front();
            if ( i >= k )
             sum+=a[dq.front()];
       }
     g << sum;

    return 0;
}