백준 2581번: 소수

문제 출처: https://www.acmicpc.net/problem/2581

소수찾기 문제 참고: http://qlyh8.tistory.com/142?category=731166

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.ArrayList;
 
public class Main {
    public static void main(String[] args) throws Exception {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        int M = Integer.parseInt(reader.readLine());
        int N = Integer.parseInt(reader.readLine());
        ArrayList<String> list = new ArrayList<>();
        int sum = 0;
        
        for(int i=M ; i<=N ; i++){
            if(i==1)
                continue;
            
            boolean isPrime = true;
            for(int j=2; j<=(int)Math.sqrt(i) ; j++){
                if(i%j == 0){
                    isPrime = false;
                    break;
                }
            }
            if(isPrime){
                list.add(String.valueOf(i));
                sum += i;
            }
        }
        
        if(list.isEmpty())
            System.out.println("-1");
        else 
            System.out.println(sum + "\n" + list.get(0));
    }
}