#include <bits/stdc++.h>
using namespace std;

const int MAXN = 5e6 + 5;

int n, k, a[MAXN];
deque<int> dq;

int main() {
    ifstream cin("deque.in");
    ofstream cout("deque.out");
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);

    cin >> n >> k;
    for (int i = 1; i <= n; i++) {
        cin >> a[i];
    }

    long long sum = 0;
    for (int i = 1; i <= n; i++) {
        while (!dq.empty() && dq.front() < i - k + 1) {
            dq.pop_front();
        }
        while (!dq.empty() && a[dq.back()] >= a[i]) {
            dq.pop_back();
        }
        dq.push_back(i);
        if (i >= k) {
            sum += a[dq.front()];
        }
    }

    cout << sum << "\n";
    return 0;
}