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

using namespace std;

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

const int NMAX = 5000000 + 1;

int n, k;
deque <int> D;
int v[NMAX];

void rezolva() {
    int x, s = 0;
    for (int i = 1; i <= n; i++) {
        f >> v[i];
        while (!D.empty() && v[i] < v[D.back()]) D.pop_back();
        D.push_back(i);
        if (i >= k) {
            s += v[D.front()];
        }
        if (i - D.front() + 1 == k) D.pop_front();
    }
    g << s << '\n';
}

int main() {
    f >> n >> k;
    rezolva();
    return 0;
}