[백준] 1927번 최소 힙

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 NumberFormatException, IOException {
    	
    	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    	StringBuilder sb = new StringBuilder();
    	
    	int N = Integer.parseInt(br.readLine());
    	PriorityQueue<Integer> pq = new PriorityQueue<>();
    	
    	for(int i=0; i<N; i++) {
    		int input = Integer.parseInt(br.readLine());
    		if(input == 0) {
    			if(pq.isEmpty()) {
    				sb.append(0).append("\n");
    			}else {
    				sb.append(pq.poll()).append("\n");	
    			}		
    		}else {
    			pq.add(input);
    		}
    		
    	}
    	
    	System.out.println(sb);
    	
    }
        

}