#include <bits/stdc++.h>
using namespace std;
vector <int> t[2];
int mod(int x){
    return ((x%3)+3)%3;
}
int sgn(int x){
    if(x>0) return 1;
    else return -1;
}
int main(){
    long long s = 0;
    int n, x; cin >> n;
    for(int i = 0 ; i < n ; i++){
        cin >> x;
        if(x == 0) continue;
        else if(mod(x) == 1) t[(1-sgn(x))/2].push_back(abs(x));
        else if(mod(x) == 2) t[(1+sgn(x))/2].push_back(abs(x));
        if(x > 0) s+=x;
    }
    for(int i = 0 ; i < 2 ; i++){
        t[0].push_back(10000000);
        t[1].push_back(10000000);
    }
    sort(t[0].begin(), t[0].end());
    sort(t[1].begin(), t[1].end());
    if(s%3 == 2) s-=min((t[1][0] + t[1][1]), t[0][0]);
    else if(s%3 == 0) s-=min((t[0][0] + t[0][1]), t[1][0]);
    cout << s;
}