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

    deque<int> dq;
    long long suma = 0;

    for (int i = 1; i <= n; i++) {
        while (!dq.empty() && v[dq.back()] >= v[i]) {
            dq.pop_back();
        }
        dq.push_back(i);

        if (dq.front() <= i - k) {
            dq.pop_front();
        }

        if (i >= k) {
            suma += v[dq.front()];
        }
    }

    fout << suma;
}