import java.util.*;

public class _11286{
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        PriorityQueue<Integer> absHeap = new PriorityQueue<>((a,b) -> {
            if(Math.abs(a) == Math.abs(b)) {
                return a - b;
            }
            return Math.abs(a) - Math.abs(b); 
        });
        int N = sc.nextInt();

        for(int i = 0; i<N; i++){
            int op = sc.nextInt();
            if(op==0) System.out.println(absHeap.isEmpty() ? 0 : absHeap.poll());
            else absHeap.add(op);
        }
        
        sc.close();
    }
}