#include <fstream>
#include <deque>

using namespace std;

ifstream in ("deque.in");
ofstream out ("deque.out");

int n, k;

long long v[5000137];

long long sorin;

deque < int > dq;

int main()
{
    in >> n >> k;
    for ( register int i = 1 ; i <= n ; ++i )
    {
        in >> v[i];
        while ( !dq.empty ()  &&  v[dq.back ()] >= v[i] )
            dq.pop_back ();
        dq.push_back (i);
        if ( dq.front () == i - k )
            dq.pop_front ();
        if ( i >= k )
            sorin += v[dq.front ()];
    }
    out << sorin;
    return 0;
}