#include <fstream>
#include <deque>

using namespace std;

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

long long nr[5000500];
deque <int> D;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(NULL);

    long long cont = 0;
    int n, k;
    cin >> n >> k;
    for (int i = 1; i <= n; i++) {
        cin >> nr[i];
    }
    for (int i = 1; i <= n; i++) {
        while (!D.empty() && D.front() <= i - k) {
            D.pop_front();
        }
        while (!D.empty() && nr[D.back()] > nr[i]) {
            D.pop_back();
        }
        D.push_back(i);
        if (i >= k) {
            cont += nr[D.front()];
        }
    }
    cout << cont;
    return 0;
}