#include <bits/stdc++.h>

using namespace std;
#define endl '\n'
using ll = long long;

const int N = 1e5 + 10;

int n;
ll a[N], pre[N], cost[N];
int lst[N], lim[N], nxt[N];

struct Node {
    ll lmi, rmi, mi, sum;
};

class Segment {
private:
    ll a[N];
    Node node[N << 2];
public:
    void init (int n, ll num[]) {
        for (int i = 1; i <= n; i ++) a[i] = num[i];
    }
    void build (int s, int t, int p) {
        if (s == t) {
            node[p].sum = a[s];
            node[p].mi = node[p].lmi = node[p].rmi = min(0LL, a[s]);
            return;
        }
        int mid = (s + t) >> 1;
        build(s, mid, p << 1);
        build(mid + 1, t, p << 1 | 1);
    }
    Node merge (Node &x, Node &y) {
        Node res;
        res.sum = x.sum + y.sum;
        res.lmi = min(x.sum + y.lmi, x.lmi);
        res.rmi = min(x.rmi + y.sum, y.rmi);
        res.mi = min(x.mi, y.mi);
        res.mi = min(res.mi, x.rmi + y.lmi);
        return res;
    }
    void pushup(int p) {
        node[p] = merge(node[p << 1], node[p << 1 | 1]);
    }
    Node query (int l, int r, int s, int t, int p) {
        if (l <= s && t <= r) {
            return node[p];
        }
        int mid = (s + t) >> 1;
        Node res1, res2;
        if (l <= mid) res1 = query(l, r, s, mid, p << 1);
        if (mid < r) res2 = query(l, r, mid + 1, t, p << 1 | 1);
        return merge(res1, res2);
    }
};
Segment seg;

void solve () {
    cin >> n;
    int last = 0;
    cost[0] = 0;
    pre[0] = 0;
    ll mi = 0;
    for (int i = 1; i <= n; i ++) {
        cin >> a[i];
        pre[i] = pre[i - 1] + a[i];
        cost[i] = cost[i - 1] + pre[i];
        mi = min(cost[i] - cost[last], mi);
//      cout << i << ' ' << last << ' ' << mi << endl;
        if (pre[i] > pre[last]) {
            nxt[last] = i;
            lim[i] = mi;
            last = i;
            mi = 0;
        }
    }
    if (last != n) {
        nxt[last] = n;
        lim[n] = mi;
    }
    if (lim[nxt[0]] < 0 || pre[n] < 0) {
        cout << "-1\n";
        return;
    }

//  cout << "debug\n";
//  for (int i = 0; i <= n; i ++) {
//      cout << i << " : " << nxt[i] << ' ' << lim[nxt[i]] << endl;
//  }

    int p = 0;
    ll ans = 0;
    ll sum = 0;
    while (p < n) {
        if (lim[p[nxt]] + sum < 0) {
            ll need = -sum - lim[p[nxt]];
            ll d = (need + pre[p] - 1) / pre[p];
//          cout << d << endl;
            ans += d;
            sum += pre[p] * d;
        }
        sum += cost[nxt[p]] - cost[p];
        ans += nxt[p] - p;
        p = nxt[p];
//      cout << p << ' ' << ans << ' ' << sum << endl;
    }
    cout << ans << endl;
}

signed main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int _ = 1;
//  cin >> _;
    while(_ --) {
        solve();
    }
    return 0;
}