#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define Algerian ios::sync_with_stdio(false);
#define OI cin.tie(NULL);

int main (){
    Algerian OI
    int n; cin >> n;
    vector<int> a(n);
    for(auto &i : a) cin >> i;
    int seats = (n+1)/2;
    ll ans = 0;
    sort(a.begin(),a.end(),greater<int>());
    for (int i = 0; i < n && seats>0; ++i){
        if(a[i]<0) break;
        ans += a[i];
    }
    cout << ans;
}