import java.util.Scanner;
import java.util.ArrayList;

public class cozinheiro {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        ArrayList<Integer> p0 = new ArrayList<>();
        ArrayList<Integer> p1 = new ArrayList<>();
        
        for (int i = 1; i <= n; i++) {
            int x = sc.nextInt();
            if (x == 0) p0.add(i);
            else p1.add(i);
        }
        
        System.out.println(p0.size());
        for (int i = 0; i < p0.size(); i++) {
            System.out.print(p0.get(i) + (i == p0.size() - 1 ? "" : " "));
        }
        System.out.println();
        
        System.out.println(p1.size());
        for (int i = 0; i < p1.size(); i++) {
            System.out.print(p1.get(i) + (i == p1.size() - 1 ? "" : " "));
        }
        System.out.println();
        sc.close();
    }
}