我的程式：

import java.util.Scanner;

public class X {

public static void main(String[] args) {

Scanner sc = new Scanner(System.in);

int a, b, c;

a = sc.nextInt();

b = sc.nextInt();

c = sc.nextInt();

double num = Math.sqrt(b * b - 4 * a * c);

if (num < 0) {

System.out.println("No real root");

} else if (num == 0) {

System.out.println("Two same roots x=" + (-b / (2 * a)));

} else {

System.out.println("Two different roots x1="

+ ((-b + num) / (2 * a)) + " , x2="

+ ((-b - num) / (2 * a)));

}

}

}

第 1 測資點(0%): SE () 
系統錯誤

無法讀取裁判機！Server returned HTTP response code: 500 for URL:

不知道是什麼原因，請教各位大大，謝謝‧