#include <bits/stdc++.h>
using namespace std;
int main() {
    cin.tie(nullptr)->sync_with_stdio(false);
    int n, k;
    cin >> n >> k;
    vector<int> a(n + 1);
    for (int i = 1; i <= n; ++i) {
        cin >> a[i];
    }
    deque<int> dq;
    int ans = 0;
    for (int i = 1; i <= n; ++i) {
        while (!dq.empty() && a[dq.front()] >= a[i]) {
            dq.pop_front();
        }
        dq.push_front(i);
        if (i >= k) {
            ans += a[dq.back()];
            if (dq.back() == i - k + 1) {
                dq.pop_back();
            }
        }

    }
    cout << ans;
}