#include<bits/stdc++.h>
using namespace std;
#include<atcoder/all>
using namespace atcoder;
using mint=atcoder::modint998244353;

int main(){
	int n;cin>>n;
	vector<int> a(n);for(auto&&e:a)cin>>e;

	map<pair<int,bool>,int> dp;
	dp[{0,0}]=0;

	for(int i=0;i<n;i++){
		map<pair<int,bool>,int> ndp;
		for(auto&&[x,y]:dp){
			ndp[x]=max(ndp[x],y+a[i]);
			if(abs(x.first-a[i])<=3000)ndp[{x.first-a[i],1}]=max(ndp[{x.first-a[i],1}],y);
			if(abs(x.first+a[i])<=3000)ndp[{x.first+a[i],1}]=max(ndp[{x.first+a[i],1}],y);
		}
		swap(dp,ndp);
	}

	if(dp[{0,1}])cout<<dp[{0,1}]<<endl;
	else cout<<-1<<endl;
}