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#include <bits/stdc++.h>
using namespace std;

#define endl '\n'
#define L long long
#define MP make_pair
#define REP(i, n) for(int i = 0; i < n; ++i)
#define REPR(i, n) for(int i = n - 1; i >= 0; --i)
#define FOR(i, a, b) for(int i = a; i < b; ++i)
#define FORR(i, a, b) for(int i = b - 1; i >= a; --i)
#define EB emplace_back
#define ST first
#define ND second
#define S size()
#define RS resize

using VI = vector<int>;
using VVI = vector<VI>;
using PI = pair<int, int>;
using VPI = vector<PI>;
using VVPI = vector<VPI>;
using VL = vector<L>;
using VVL = vector<VL>;
using VB = vector<bool>;
using VC = vector<char>;


int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    
    int n;
    cin >> n;
    VL a(n);
    REP(i, n)
        cin >> a[i];
    
    set<pair<L, int> > s;
    s.insert(MP(0, 0));
    
    L pref = a[0];
    FOR(i, 1, n)
    {
        auto it = s.lower_bound(MP(-pref, -(2 * n)));
        if (it != s.end())
            s.insert(MP(-pref, it->ND - 1));
        pref += a[i];
    }
    
    auto it = s.lower_bound(MP(-pref, -(2 * n)));
    if (it == s.end())
        cout << -1;
    else
        cout << it->ND + n - 1;
}