#include <algorithm>
#include <numeric>
#include <cassert>
#include <deque>
#include <vector>
#include <iostream>
using namespace std;
int main() {
    int n, k; cin >> n >> k;
    vector<int> a(n);
    for (int i = 0; i < n; i++) cin >> a[i];
    deque<int> q;
    vector<long long> dp(n + 1);
    q.push_back(0);
    dp[0] = 0;
    for (int i = 1; i <= n; ++i) {
        while (q.front() + k < i) q.pop_front();
        assert(!q.empty());
        dp[i] = (q.front() == -1 ? 0 : dp[q.front()]) + a[i - 1];
        while (!q.empty() && dp[q.back()] >= dp[i]) q.pop_back();
        q.push_back(i);
    }
    cout << reduce(a.begin(), a.end(), 0LL) - *min_element(dp.rbegin(), dp.rbegin() + k) << '\n';
}