[백준 5597] 과제 안 내신 분..?

문제

https://www.acmicpc.net/problem/5597

5597번: 과제 안 내신 분..?

---

내가 작성한 코드

import java.io.*;
import java.util.*;

public class 백준5597 {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));

        Set<Integer> student = new HashSet<>();
        for(int i = 1; i<=30; i++){
            student.add(i);
        }

        for(int i = 0; i<28; i++){
            student.remove(Integer.parseInt(br.readLine()));
        }

        Iterator<Integer> result = student.iterator();

        for(int i = 0; i<2; i++){
            bw.write(Integer.toString(result.next()));
            bw.newLine();
        }

        bw.close();
    }
}