#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);
    for (int i = 0; i < n; ++i) {
        fin >> v[i];
    }
    long long sum = 0;
    vector<int> dq(n);
    int front = 0, back = -1;
    for (int i = 0; i < n; ++i) {
        while (front <= back && dq[front] <= i - k) {
            ++front;
        }
        while (front <= back && v[dq[back]] >= v[i]) {
            --back;
        }
        dq[++back] = i;
        if (i >= k - 1) {
            sum += v[dq[front]];
        }
    }
    fout << sum;
    return 0;
}