#include <bits/stdc++.h>
#define REP(i, n) for (int i = 0; (i) < (int)(n); ++(i))
#define REP3(i, m, n) for (int i = (m); (i) < (int)(n); ++(i))
#define REP_R(i, n) for (int i = (int)(n)-1; (i) >= 0; --(i))
#define REP3R(i, m, n) for (int i = (int)(n)-1; (i) >= (int)(m); --(i))
#define ALL(x) ::std::begin(x), ::std::end(x)
using namespace std;
template <class T> using reversed_priority_queue = priority_queue<T, vector<T>, greater<T> >;

int64_t solve(int n, int64_t k, const vector<int64_t>& a) {
    if (k == 1) return a[0];

    vector<int64_t> min_a(n + 1, INT64_MAX);
    REP_R (i, n) {
        min_a[i] = min(min_a[i + 1], a[i]);
    }

    int64_t ans = INT64_MAX;
    priority_queue<pair<int64_t, int> > que;
    int64_t sum_que = 0;
    set<int> indices_que;
    reversed_priority_queue<pair<int64_t, int> > revque;
    REP3R (i, k - 1, n) {
        int q = i / (k - 1);
        int r = i % (k - 1);
        int m = q + (not not r) - 1;
        if (k * (m + 1) <= n and m <= que.size() + revque.size()) {
            while (not que.empty() and ((que.size() > m) or (not revque.empty() and que.top().first > revque.top().first))) {
                int j = que.top().second;
                que.pop();
                sum_que -= a[j];
                indices_que.erase(j);
                revque.emplace(a[j], j);
            }
            while (que.size() < m) {
                assert (not revque.empty());
                int j = revque.top().second;
                revque.pop();
                que.emplace(a[j], j);
                sum_que += a[j];
                indices_que.insert(j);
            }
            assert (que.size() == m);
            if (not indices_que.empty() and *indices_que.rbegin() < k * m) {
                int j = que.top().second;
                ans = min(ans, a[i] + sum_que - a[j] + min_a[k * m]);
            } else {
                ans = min(ans, a[i] + sum_que);
            }
        }
        que.emplace(a[i], i);
        sum_que += a[i];
        indices_que.insert(i);
    }
    return ans;
}

// generated by online-judge-template-generator v4.7.1 (https://github.com/online-judge-tools/template-generator)
int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    constexpr char endl = '\n';
    int64_t N;
    int64_t K;
    cin >> N;
    vector<int64_t> A(N);
    cin >> K;
    REP (i, N) { cin >> A[i]; }
    auto ans = solve(N, K, A);
    cout << ans << endl;
    return 0;
}