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

using namespace std;

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

    int n, k;
    in >> n;
    in >> k;
    //k--;

    vector<int> v;
    v.reserve(n + 1);

    for (int i = 1; i <= n; i++) {
        in >> v[i];
    }

    deque<int> d;
    long long sum = 0;
    for (int i = 1; i <= n; 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) sum += v[d.front()];
    }

    out << sum << "\n";

    return 0;
}