vector<int> ans;

int main() {
    int n;
    cin >> n;
    vector<int> a(n);
    for (auto &i:a)
        cin>>i;
    memset(in, 0, sizeof in);
    int day = 1;
    for (int i= 0; i< a.size(); ++i) {
        update (abs(a[i]), sign(a[i]));
        // employee already entered that day and is entering
        if (in[abs(a[i])] == day && a[i] > 0) {
            cout << -1 << endl;
            return 0;
        }
        // employee didnt entered that day and is leaving
        if (in[abs(a[i])] < day && a[i] < 0) {
            cout << -1 << endl;
            return 0;
        }
        // employee entered that day
        if (a[i] > 0)
            in[a[i]] = day;
        int q = query();
        // office is empty new day starts
        if (q == 0) {
            ans.pb(i+1);
            day++;
        }
    }
    // office is not empty
    int q = query();
    if (q != 0)
        cout << -1 << endl;
    else {
        cout << ans.size() << endl;
        for (int i= 0; i< ans.size(); ++i) {
            if (i) {
                cout << " " << ans[i]-ans[i-1];
            } else
                cout << ans[i];
        }
        cout << '\n';
    }

    return 0;
}