#include <bits/stdc++.h>

using namespace std;

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

int n, k, a[5000005];
long long sum;
deque<int> d;

int main() {
    fin >> n >> k;
    for (int i = 1; i <= n; i++) {
        fin >> a[i];
        while (!d.empty() && a[d.back()] > a[i]) {
            d.pop_back();
        }
        d.push_back(i);
        if (i - d.front() == k) {
            d.pop_front();
        }

        if (i >= k) {
            sum += (long long)a[d.front()];
        }
    }
    fout << sum;
}