[백준] 7785번 회사에 있는 사람

import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Scanner;
public class Main {
	
	public static void main(String[] args){
		Scanner kb = new Scanner(System.in);
		int n = kb.nextInt();
		
		HashMap<String, Integer> map = new HashMap<>();
		
		for(int i=0; i<n; i++) {
			String name = kb.next();
			String status = kb.next();
			
			if(status.equals("enter")) {
				map.put(name, map.getOrDefault(name, 0)+1);
			}else {
				map.remove(name);
			}
		}
		
		List<String> list = new ArrayList<>();
		
		for(String x: map.keySet()) {
			list.add(x);
		}
		
		Collections.sort(list, Collections.reverseOrder());
		
		for(String x: list) {
			System.out.println(x);
		}

	}
}