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#include <iostream>
#include <set>
#include <vector>
#include <utility>
#include <map>
#include <queue>
#include <algorithm>
#include <string>
#include <map>
using namespace std;
#define PB push_back
#define MP make_pair
#define F first
#define S second
typedef long long ll;
typedef pair<int, int> pii;
const int INF = 1e9;

int n, P = 1;

vector<ll> v, soso;
vector<pair<int, pair<ll, int>>> positive;
set<int> ms;
// pozycja, suma, liczba

vector<int> tree;

void buildTree(int x) {
    while (P < x) {
        P *= 2;
    }

    tree.resize(2 * P, 0);
}

int query(int a, int b) {
    if (a > b) {
        return 0;
    }
    a += P - 1;
    b += P - 1;
    int res = max(tree[a], tree[b]);

    while (a / 2 != b / 2) {
        if (a % 2 == 0) res = max(res, tree[a + 1]);
        if (b % 2 == 1) res = max(res, tree[b - 1]);
        a /= 2;
        b /= 2;
    }
    return res;
}

void insert(int pos, int res) {
    pos += P - 1;
    tree[pos] = max(tree[pos], res);
    pos /= 2;
    while (pos) {
        tree[pos] = max(tree[2 * pos], tree[2 * pos + 1]);
        pos /= 2;
    }
}

void solve() {
    cin >> n;

    v.resize(n + 1, 0);
    for (int i = 0; i < n; i++) {
        cin >> v[i + 1];
    }

    int zero = 0;
    bool addZero = true;
    ll sum = 0;
    for (int i = 1; i <= n; i++) {
        
        if (v[i]) {
            addZero = false;
            sum += v[i];
            if (sum >= 0) {
                positive.PB(MP(i, MP(sum, 1)));
                soso.PB(sum); 
                addZero = true;
            }
            zero = 0;
        }
        else {
            zero++;
            if (addZero && positive.size()) {
                positive[positive.size() - 1].S.S++;
            }
        }
    }

    if (positive.size() == 0) {
        cout << -1 << endl;
        exit(0);
    }

    positive[positive.size() - 1].S.S = 0;

    sort(soso.begin(), soso.end());
    soso.erase(unique(soso.begin(), soso.end()), soso.end());

    vector<pii> good;
    vector<ll>::iterator it;
    for (pair<int, pii> p : positive) {
        it = lower_bound(soso.begin(), soso.end(), p.S.F);
        ll dist = (it - soso.begin());
        dist++;
        good.PB(MP(dist, p.S.S));
    }

    buildTree(good.size());
    vector<int> res(good.size(), 0);

    for (int i = 0; i < good.size(); i++) {
        pii p = good[i];
        int q = query(1, p.F);
        res[i] = q + p.S;
        insert(p.F, res[i]);
    }
    cout << n - 1 - res[good.size() - 1] - zero << endl;
}

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(NULL);
    cout.tie(NULL);

    solve();

    return 0;
}