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

using namespace std;

void calculeaza_suma_minima(int n, int k, const vector<int>& a, ofstream& fout) {
    deque<int> d;
    long long rez = 0;
    d.push_back(0);
    for (int i = 1; i < n; i++) {
        while (!d.empty() && a[d.back()] >= a[i])
            d.pop_back();
        d.push_back(i);
        if (d.front() <= i - k)
            d.pop_front();
        if (i >= k - 1)
            rez += a[d.front()];
    }
    fout << rez;
}

int main()
{
    ifstream fin("deque.in");
    ofstream fout("deque.out");

    int n, k;
    fin >> n >> k;
    vector<int> a(n);
    for (int i = 0; i < n; i++) {
        fin >> a[i];
    }

    calculeaza_suma_minima(n, k, a, fout);

    fin.close();
    fout.close();

    return 0;
}