#include<bits/stdc++.h>
#define F(i, a, b) for(int i = a; i <= b; i ++)
#define Fd(i, a, b) for(int i = a; i >= b; i --)
#define pb push_back
#define pii pair<int, int>
#define fi first
#define se second
#define int long long
using namespace std;
 
const int mod = 998244353;
const int N = 5e5 + 10;
const int inf = 1e18;
typedef array<int, 3> a3; 
typedef long long ll;
 
int n, m, a[N];
 
void sol() {
    cin >> n;
    F(i, 1, n) cin >> a[i];
    vector<int> res;
    F(i, 1, n) {
        if(a[i] >= 0) res.push_back(a[i]);
        else if(res.size() && res.back() >= 0) res.push_back(a[i]);
    }
    int ans = 0;
    for(int i = 1; i < res.size(); i ++) {
        ans += max(res[i], res[i - 1]);
    }
    cout << ans << '\n';
}   
 
signed main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int t = 1;
    F(i, 1, t) sol();
    return 0;
}