import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.PriorityQueue;
public class Main {
public static void main(String[] args) throws IOException {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
int N = Integer.parseInt(br.readLine());
PriorityQueue<Integer> queue = new PriorityQueue<>((o1, o2) -> {
int first = Math.abs(o1);
int second = Math.abs(o2);
if(first == second) {
return o1 > o2 ? 1 : -1;
} else {
return first - second;
}
});
for(int i=0; i<N; i++) {
int num = Integer.parseInt(br.readLine());
if(num == 0) {
if(queue.isEmpty()) System.out.println("0");
else System.out.println(queue.poll());
} else {
queue.add(num);
}
}
}
}