#include <iostream>
#include <fstream>
#include <deque>

using namespace std;

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

int n, k;
long long sol;
int v[5000001];
deque <int> dq;

int main () {
    f >> n >> k;
    for (int i = 1; i <= n; i++) {
        f >> v[i];
        while (!dq.empty() && v[i] <= v[dq.back ()])
            dq.pop_back ();
        dq.push_back (i);
        if (dq.front () == i - k) dq.pop_front ();
        if (i >= k) sol +=v[dq.front ()];
    }
    g << sol << '\n';
    return 0;
}