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

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

int a[5000005];
deque<int> D;
int n, k;
long long sum;

int main()
{
    is >> n >> k;
    for ( int i = 1; i <= n; ++i )
        is >> a[i];
    for ( int i = 1; i <= n; ++i )
    {
        while ( !D.empty() && a[D.back()] >= a[i] )
            D.pop_back();
        D.push_back(i);

        while ( D.front() <= i - k )
            D.pop_front();

        if ( i >= k )
            sum += a[D.front()];
    }

    os << sum;
    is.close();
    os.close();
    return 0;
}