#include <bits/stdc++.h>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
//const int INF = 1e9;
//const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n) - 1; i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r) - 1;i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int n; cin >> n;
	vector<int>a(n);
	rep(i, n)cin >> a[i];
	int lim = 5000;
	if (n <= 20)lim *= 20;
	else if (n <= 200)lim *= 10;
	else lim *= 2;
	vector dp(n + 1, vector<int>(lim + 1));
	dp[0][0] = 1;
	rep(i, n)rep(j, lim + 1) {
		{
			int ni = i + 1;
			int nj = j;
			dp[ni][nj] += dp[i][j];
			chmin(dp[ni][nj], 2);
		}
		{
			int ni = i + 1;
			int nj = j + a[i];
			if (nj <= lim) {
				dp[ni][nj] += dp[i][j];
				chmin(dp[ni][nj], 2);
			}
		}
	}
	int ans = 0;
	rep(i, n)ans += a[i];
	int x = -1;
	rrep(i, lim + 1) {
		if (i * 2 == ans)continue;
		if (dp[n][i] == 2)x = i;
	}
	ans -= x * 2;
	if (-1 == x)ans = -1;
	cout << ans << endl;
	return 0;
}