#include <bits/stdc++.h>
using namespace std;

long long n, k, m;
long long a[200000], d[200000];
priority_queue<long long, vector<long long>, greater<long long>> Q;

int main() {    
    cin >> n >> k;

    for (int i = 0; i < n; i++)
        cin >> a[i];

    for (int i = n - 1; i > 0; i--) {
        d[i - 1] = d[i];

        if (Q.size() < k - 1) {
            Q.push(a[i]);
            d[i - 1] += a[i];
        }
        else {
            long long t = Q.top();

            if (t < a[i]) {
                Q.pop();
                Q.push(a[i]);
                d[i - 1] += a[i] - t;
            }
        }
    }

    for (int i = 1; i < n; i += 2)
        m = max(m, a[i] + d[i]);

    cout << m << endl;
}