#include <iostream>
#include <cmath>
#include <algorithm>
#include <queue>
#include <vector>
#include <map>
#include <set>
#include <unordered_set>
#include <stack>
#include <iomanip>
#include <cstring>
#include <string>
#include <cstdio>
// #include <bits/stdc++.h>

#pragma GCC push_options
#pragma GCC optimize ("O0")

using namespace std;

typedef string str;
typedef long long ll;
typedef double db;
typedef long double ld;
typedef unsigned long long ull;
typedef pair <int, int> pii;
typedef pair <ll, ll> pll;
typedef pair <db, db> pdd;
typedef pair <ld, ld> pld;
typedef ll var;
typedef pair <var, var> pvv;


#define sync ios_base::sync_with_stdio(false)
#define printbool cout << (solve() ? "YES" : "NO") << '\n'
#define updiv(ad, bd) (((ad - 1) / bd ) + 1)
#define mod(ad, bd) ((((ad) % (bd)) + (bd)) % (bd))
#define mxz(ad, bd) ad = max( ad, bd )
#define mnz(ad, bd) ad = min( ad, bd )
#define maxx(ad, bd, c) max(ad, max(bd, c))
#define minn(ad, bd, c) min(ad, min(bd, c))
#define arr(ad, bd, cd) (ad + bd), (ad + bd +cd)
#define all(ad) ad.begin(), ad.end()
#define sorts(ad) sort(all(ad))
#define sorta(ad, bd, cd) sort(arr(ad, bd, cd))
#define rvs(ad) reverse(all(ad))
#define rva(ad, bd, cd) reverse(arr(ad, bd, cd))
#define gl(ad) getline(cin, ad)
#define wfloat(ad) fixed << setprecision(ad)
#define pr(ad, bd) pair <(ad), (bd)>
#define mlx(ad, bd) max(1ll * (ad), 1ll * (bd))
#define mln(ad, bd) min(1ll * (ad), 1ll * (bd))

template <typename T>
inline T gcd(T a, T b) { while (b != 0) swap(b, a %= b); return a; }

#define SD "\033[1m\033[31m"
#define ED "\033[0m"
#define RESET   "\033[0m"
#define BLACK   "\033[30m"      /* Black */
#define RED     "\033[31m"      /* Red */
#define GREEN   "\033[32m"      /* Green */
#define YELLOW  "\033[33m"      /* Yellow */
#define BLUE    "\033[34m"      /* Blue */
#define MAGENTA "\033[35m"      /* Magenta */
#define CYAN    "\033[36m"      /* Cyan */
#define WHITE   "\033[37m"      /* White */
#define BOLDBLACK   "\033[1m\033[30m"      /* Bold Black */
#define BOLDRED     "\033[1m\033[31m"      /* Bold Red */
#define BOLDGREEN   "\033[1m\033[32m"      /* Bold Green */
#define BOLDYELLOW  "\033[1m\033[33m"      /* Bold Yellow */
#define BOLDBLUE    "\033[1m\033[34m"      /* Bold Blue */
#define BOLDMAGENTA "\033[1m\033[35m"      /* Bold Magenta */
#define BOLDCYAN    "\033[1m\033[36m"      /* Bold Cyan */
#define BOLDWHITE   "\033[1m\033[37m"      /* Bold White */
#define sdebug cout << BOLDRED
#define edebug cout << RESET

#ifdef DEBUG
void debug(const auto &c, const auto &e, const auto &... r) {
  cout << c << e;
  ((cout << " " << r), ..., (cout << ED << endl));
}
void dout(const auto &c, const auto &e, const auto &... r) {
  cout << c << e;
  ((cout << " " << r), ..., (cout << ED << " "));
}
#else
#define debug(...)
#define dout(...)
#endif

// cerr << 1.0 * clock() / CLOCKS_PER_SEC << endl;

#define rv reverse
#define cl clear
#define nl endl
#define pb push_back
#define pf push_front
#define ppb pop_back
#define ppf pop_front
#define pu push
#define pp pop
#define in insert
#define er erase
#define mp make_pair
#define popcnt __builtin_popcount
#define np next_permutation
#define lb lower_bound // <=
#define ub upper_bound // <
#define rand mt19937_64
#define tp top
#define ft front
#define et empty
#define sz size
#define op operator
#define f first
#define s second
#define y1 yyyyy
#define cont continue
// #define x first
// #define y second

// freopen("text.in", "r", stdin);
// freopen("text.out", "w", stdout);

// pii dr[8] = { mp(2, 1), mp(2, -1), mp(-2, 1), mp(-2, -1), mp(1, 2), mp(1, -2), mp(-1, 2), mp(-1, -2) };

const int dx[] = {0, 1, 0, -1, 1, -1, -1, 1};
const int dy[] = {1, 0, -1, 0, 1, -1, 1, -1};

const ll LINF = 1e18; //infinity
const double EPS = 1e-6 ; //epsilon
const double PI = 3.14159; //pi
const ll B = 31 ; //hashbase
const ll LG = 11; //logarithm
const ll INF = 1e9; //infinity
const ll M = 1e9 + 7; //mod
const ll N = 1e6 + 9; //maxn

int n;
int a[N];
set <int> v;
map <int, int> ma;
int ans = -1;

void solve(int l, int r, int i) {
    if (i == n/2+1) {
        v.in(l-r);
        mxz(ma[l-r], r);
        return;
    }
    solve(l+a[i], r, i+1);
    solve(l, r+a[i], i+1);
    solve(l, r, i+1);
}

void solve2(int l, int r, int i) {
    if (i == n+1) {
        if (v.find(r-l) != v.end()) {
            if (r+ma[r-l] > 0)
                mxz(ans, r+ma[r-l]);
        }
        return;
    }
    solve2(l+a[i], r, i+1);
    solve2(l, r+a[i], i+1);
    solve2(l, r, i+1);
}

int main() {
    sync;
    cin >> n;
    for (int i = 1; i <= n; ++i) {
        cin >> a[i];
    }
    solve(0, 0, 1);
    solve2(0, 0, n/2+1);
    cout << ans << '\n';
}