#include <iostream>
#include <fstream>
#include <deque>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
deque <int> q;
int n, k, el, i, j, ultimul_min, v[5000005];
long long sum;

void input() {
    fin >> n >> k;
    for (i = 1; i <= n; ++i)
        fin >> v[i];
}

void modifUltimulMin() {
    if (j == n - k + 1)
        ultimul_min = v[n - k + 1];
    if (j > n - k + 1 && ultimul_min > v[j])
        ultimul_min = v[j];
}

void modifSumaSiEliminareEl() {
    if (j > k) {
        ++i;
        if (!q.empty()) {
            sum += v[q.front()];
            while (q.front() < i) {
                q.pop_front();
                if (q.empty())
                    break;
            }
        }
    }
}

void adaugaEl() {
    if (!q.empty())
        while (v[j] < v[q.back()]) {
            q.pop_back();
            if (q.empty())
                break;
        }
    q.push_back(j);
}

int main() {
    input();
    for (j = 1, i = 1; j <= n; ++j) {
        modifUltimulMin();
        modifSumaSiEliminareEl();
        adaugaEl();
    }
    fout << sum + ultimul_min;
    return 0;
}