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#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using Pii = pair<int,int>;
using Vi = vector<int>;
#define mp make_pair
#define pb push_back
#define x first
#define y second
#define rep(i,b,e) for (int i = (b); i < (e); i++)
#define each(a,x) for (auto& a : (x))
#define all(x) (x).begin(),(x).end()
#define sz(x) int((x).size())
#define endl '\n'

const int inf = 1e9;

struct Tree {
    int base = 1;
    vector<int> mini;
    Tree(int n) {
        while (base < n) base *= 2;
        mini.resize(2 * base, inf);
    }
    void insert(int a, int c) {
        a += base;
        mini[a] = min(mini[a], c);
        a /= 2;
        while (a >= 1) {
            mini[a] = min(mini[2*a], mini[2*a + 1]);
            a /= 2;
        }
    }
    int query(int a, int b) {
        a += base;
        b += base;
        int res = min(mini[a], mini[b]);
        while (a/2 != b/2) {
            if (a % 2 == 0) res = min(res, mini[a+1]);
            if (b % 2 == 1) res = min(res, mini[b-1]);
            a /= 2;
            b /= 2;
        }
        return res;
    }
};

vector<int> getPos(vector<ll> V) {
    vector<int> pos(sz(V));
    vector<pair<ll, int>> tmp;
    for (int i = 0; i < sz(V); i++) {
        tmp.push_back({V[i], i});
    }
    sort(all(tmp));
    for (int i = 0; i < sz(tmp); i++) {
        pos[tmp[i].y] = i;
    }
    return pos;
}

void solve() {
    int n;
    cin >> n;
    vector<ll> V(n+1);
    for (int i = 1; i <= n; i++) {
        cin >> V[i];
        V[i] += V[i-1];
    }
    vector<int> treePos = getPos(V);
    Tree tree(n+1);
    vector<int> dp(n+1, inf);
    dp[0] = 0;
    tree.insert(treePos[0], dp[0] - (0 + 1));
    for (int i = 1; i <= n; i++) {
        dp[i] = i + tree.query(0, treePos[i]);
        tree.insert(treePos[i], dp[i] - (i + 1));
    }
    if (dp[n] < inf) {
        cout << dp[n] << endl;
    } else {
        cout << -1 << endl;
    }
}

int main() {
    cin.sync_with_stdio(0); cin.tie(0);
    cout << fixed << setprecision(10);
    int t = 1; 
    //cin >> t;
    for (int i = 0; i < t; i++) {
        solve();
    }
}