#include <fstream>
#include <deque>

const int NMAX = 5000005;

using namespace std;

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

int N,K;
int v[NMAX];
deque <int> D;
long long sum;

int main()
{
    f >> N >> K;
    for (int i = 1; i <= N; ++i)
    {
        f >> v[i];
    }

    for (int i = 1; i <= N; ++i)
    {
        while(!D.empty() && v[D.back()] >= v[i])
        {
            D.pop_back();
        }
        D.push_back(i);

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

        if (i >= K)
            sum += v[ D.front() ];
    }

    g << sum;

    f.close();
    g.close();
    return 0;
}