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

int main() {
    std::ifstream input("deque.in");
    std::ofstream output("deque.out");

    int n, k;
    input >> n >> k;
    std::vector<int> a(n);
    long long ans = 0;

    for (int i = 0; i < n; ++i) {
        input >> a[i];
    }

    std::deque<int> dq;

    for (int i = 0; i < n; ++i) {
        while (!dq.empty() && a[i] <= a[dq.back()]) {
            dq.pop_back();
        }
        dq.push_back(i);

        if (dq.front() == i - k) {
            dq.pop_front();
        }

        if (i >= k - 1) {
            ans += a[dq.front()];
        }
    }

    output << ans;
    input.close();
    output.close();
    return 0;
}