#include <fstream>
#include <vector>
#include <list>
#include <queue>

using namespace std;

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

int  n, m, q, x, y, sol, s, v, k, l;
int a[500005];
deque<int>d;


int main()
{
    f >> n >> k;
    for (int i = 1; i <= n; i++)
    {
        f >> a[i];
        while (!d.empty() && a[i] <= a[d.back()])
        {
            d.pop_back();
        }
        d.push_back(i);
        if (d.front() == i - k) d.pop_front();
        if (i >= k)
        {
            sol += a[d.front()];
        }
    }
    g << sol << '\n';

    return 0;
}