#include <bits/stdc++.h>
#define NMAX 5000000
#define ll long long
#define ull unsigned long long

using namespace std;

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

int n, k, a[NMAX + 2];
ll sum;
deque<int> dq;

int main() {
    fin >> n >> k;
    for (int i = 1; i <= n; i++) {
        fin >> a[i];
    }

    for (int i = 1; i <= n; i++) {
        if (!dq.empty() && i - dq.front() == k) {
            dq.pop_front();
        }
        while (!dq.empty() && a[i] <= a[dq.back()]) {
            dq.pop_back();
        }
        dq.push_back(i);
        if (i >= k) {
            sum += a[dq.front()];
        }
    }
    fout << sum;
    return 0;
}