#include <iostream>
#include <vector>
#include <queue>
using namespace std;
typedef long long ll;

int main() {
    ios_base::sync_with_stdio(false);
    int n;
    cin >> n;

    vector<ll> v(n);
    for(int i = 0; i < n; i++) {
        cin >> v[i];
    }

    int K = n / 3;

    vector<ll> max_left(n, 0);
    priority_queue<ll, vector<ll>, greater<ll>> pq;

    ll current_sum = 0;
    for(int i = 0; i < n; i++) {
        pq.push(v[i]);
        current_sum += v[i];
        if((int) pq.size() > K) {
            current_sum -= pq.top();
            pq.pop();
        }

        if((int) pq.size() == K) {
            max_left[i] = current_sum;
        }
    }

    vector<ll> min_right(n, 0);
    priority_queue<ll, vector<ll>, less<ll>> pq2;
    ll right_current_sum = 0;

    for(int i = n - 1; i >= 0; i--) {
        pq2.push(v[i]);
        right_current_sum += v[i];
        if((int) pq2.size() > K) {
            right_current_sum -= pq2.top();
            pq2.pop();
        }

        if((int) pq2.size() == K) {
            min_right[i] = right_current_sum;
        }
    }

    ll res = -1e18;
    for(int i = K - 1; i <= 2 * K - 1; i++) {
        ll A = max_left[i];
        ll B = min_right[i + 1];
        res = max(res, A - B);
    }

    cout << res << endl;

    return 0;
}