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

const int N = 500100;

int n;

long long a[N], pref[N];
int t[N*4], sz;

void build(int v, int l, int r) {
    t[v] = 1e9;
    if (l == r)
        return;
    int mid = (l+r)>>1;
    build(v+v, l, mid);
    build(v+v+1, mid+1, r);
}

int get(int v, int l, int r, int tl, int tr) {
    if (l > r || tl > r || l > tr || tl > tr)
        return 1e9;
    if (tl <= l && r <= tr)
        return t[v];
    int mid = (l+r)>>1;
    return min(get(v+v, l, mid, tl, tr), get(v+v+1, mid+1, r, tl, tr));
}

void update(int v, int l, int r, int pos, int x) {
    if (l == r) {
        t[v] = min(t[v], x);
        return;
    }
    int mid = (l+r)>>1;
    if (pos <= mid)
        update(v+v, l, mid, pos, x);
    else
        update(v+v+1, mid+1, r, pos, x);
    t[v] = min(t[v+v], t[v+v+1]);
}

int nxtpos[N];

void solve() {
    cin >> n;

    vector<int> vecc;

    for (int i = 1; i <= n; i++) {
        cin >> a[i];
        pref[i] = pref[i-1] + a[i];
        vecc.push_back(pref[i]);
    }
    if (pref[n] < 0) {
        cout << -1 << "\n";
        return;
    }
    nxtpos[n+1] = n+1;
    for (int i = n; i >= 1; i--){
        nxtpos[i] = nxtpos[i+1];
        if (a[i] < 0)
            nxtpos[i] = i;
    }
    vecc.push_back(0);
    sort(vecc.begin(), vecc.end());
    vecc.erase(unique(vecc.begin(), vecc.end()));
    sz = vecc.size();
    build(1, 1, sz);

    int dprst = 0;

    int pos_zero = lower_bound(vecc.begin(), vecc.end(), 0)-vecc.begin()+1;

    update(1, 1, sz, pos_zero, 0);

    for (int i = 1; i <= n; i++) {
        int pos = lower_bound(vecc.begin(), vecc.end(), pref[i])-vecc.begin()+1;

        if (a[i] < 0)
            dprst = 1e9;

        int mn = get(1, 1, sz, 1, pos)+i-1;
        dprst = min(dprst, mn);
        update(1, 1, sz, pos, dprst-i);
    }
    cout << dprst << "\n";
    


}

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

    int tt = 1;
    
    while(tt--) {
        solve();
    }

}