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

int main() {
    fin >> n >> k;
    for (int i = 1; i <= n; ++i) {
        fin >> el;
        if (k == 1) {
            sum += el;
            continue;
        }
        if (i == 1) {
            q.push_back(el);
            continue;
        }
        int el_sterse = 0;
        while (!q.empty()) {
            if (q.back() > el) {
                q.pop_back();
                ++el_sterse;
            }
            else
                break;
        }
        q.insert(q.end(), el_sterse, el);
        q.push_back(el);
        if (i >= k && !q.empty()) {
            sum += q.front();
            q.pop_front();
        }
    }
    fout << sum;
    return 0;
}