#include <iostream>
#include <vector>
#include <algorithm>
#include <limits.h>
using namespace std;

const long long inf = LLONG_MAX / 2;

int main() {
    int n;
    cin >> n;
    vector<int> a(n);
    for (int i = 0; i < n; i++) cin >> a[i];
    sort(a.begin(), a.end());

    vector<long long> dp0(40001, -inf);
    vector<long long> dp1(40001, -inf);

    dp0[0] = 0;

    for (int i = 0; i < n; i++) {
        vector<long long> new_dp0 = dp0;
        vector<long long> new_dp1 = dp1;

        for (int j = 0; j <= 40000; j++) {
            if (dp0[j] != -inf) {
                new_dp0[j] = max(new_dp0[j], dp0[j] + a[i]);
            }

            if (dp1[j] != -inf) {
                new_dp1[j] = max(new_dp1[j], dp1[j] + a[i]);
                new_dp1[abs(j - a[i])] = max(new_dp1[abs(j - a[i])], dp1[j]);
            }

            if (dp0[j] != -inf) {
                new_dp1[abs(j - a[i])] = max(new_dp1[abs(j - a[i])], dp0[j]);
            }

            if (j + a[i] <= 40000) {
                if (dp1[j] != -inf) {
                    new_dp1[j + a[i]] = max(new_dp1[j + a[i]], dp1[j]);
                }
                if (dp0[j] != -inf) {
                    new_dp1[j + a[i]] = max(new_dp1[j + a[i]], dp0[j]);
                }
            }
        }

        dp0 = new_dp0;
        dp1 = new_dp1;
    }

    cout << (dp1[0] <= 0 ? -1 : dp1[0]) << endl;

    return 0;
}