#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;
long long sol;
int v[NMAX];
deque <int> D;

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

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