[백준/자바] 5597 - 과제 안 내신 분..?

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        int[] students = new int[31];

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

        for(int i=1; i<=30; i++){
            if(students[i] == 0) System.out.println(i);
        }

        br.close();
    }
}