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

using namespace std;

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

pair<int, int> getMin(deque<pair<int, int>>& deq, int currentIndex, int k) {
    while (!deq.empty() && (deq.front().second > currentIndex || deq.front().second <= currentIndex - k)) {
        deq.pop_front();
    }
    return deq.front();
}

void insert(deque<pair<int, int>>& deq, pair<int, int> p) {
    while (!deq.empty() && deq.back().first >= p.first) {
        deq.pop_back();
    }
    deq.push_back(p);
}

int main() {
    int n, k;
    
    f >> n >> k;
    vector<int> a;
    a.resize(n);
    
    for (int i = 0; i < n; i++) {
        f >> a[i];
    }
    
    long ans = 0;

    deque<pair<int, int>> deck;

    for (int i = 0; i < n; i++) {
        insert(deck, {a[i], i});
        pair<int, int> best = getMin(deck, i, k);

        if (i >= k - 1) {
            ans += best.first;
        }

    }

    g << ans;
    g.close();

    return 0;
}