#include <bits/stdc++.h>

using namespace std;

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

int main() {
    int n, k;
    fin >> n >> k;
    vector <int> v(n + 1);
    deque <int> dq;
    long long sol = 0;
    for (int i = 1; i <= n; i++) {
        fin >> v[i];
        while (!dq.empty() && v[i] <= v[dq.back()])
            dq.pop_back();
        dq.push_back(i);
        if (dq.front() == i - k)
            dq.pop_front();
        if (i >= k)
            sol += v[dq.front()];
    }
    fout << sol << "\n";
    return 0;
}