#include <bits/stdc++.h>

using namespace std;

long long n, k, sum, v[5000005];
deque<int> dq;

int main() {

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

    f >> n >> k;

    for (int i = 1; i <= n; i++) {
        f >> v[i];
    }

    for (int i = 1; i <= n; i++) {
        while (!dq.empty() && (v[dq.back()] >= v[i])) {
            dq.pop_back();
        }

        dq.emplace_back(i);

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

        if (i >= k) {
            sum += v[dq.front()];
        }
    }

    g << sum;
}