import java.util.*;
public class Main {
    public static void main(String args[]){
        ArrayList<Integer> al = solve();
        if (al.size() == 0 || al.get(0) == -1) System.out.println("-1");
        else {
            System.out.println(al.size());
            for (int i = 0; i < al.size(); i++){
                System.out.print(al.get(i) + " ");
            }
        }
    }
    public static ArrayList<Integer> solve(){
        ArrayList<Integer> sol = new ArrayList<Integer>();
        ArrayList<Integer> al = new ArrayList<Integer>();
        Scanner in = new Scanner(System.in);
        int n = in.nextInt(), sum = 0, cut = 0;
        for (int i = 1; i <= n; i++){
            int num = in.nextInt();
            sum += num;
            if (al.contains(num)){
                sol = new ArrayList<Integer>();
                sol.add(-1);
                return sol;
            }
            if (num > 0) al.add(num);
            if (sum == 0){
                al = new ArrayList<Integer>();
                sol.add(i - cut);
                cut = i;
            }
        }
        if (sum != 0){
            sol = new ArrayList<Integer>();
            sol.add(-1);

        }
        return sol;
    }
}