CCC 2013 - Problem J1: Next In Line

I actually wrote this contest and I wrote it in VB. Here is a link to my raw solution.

The problem:

You know a family with three children. Their ages form an arithmetic sequence: the difference in ages between the middle child and youngest child is the same as the difference in ages between the oldest child and the middle child. For example, their ages could be 5, 10 and 15, since both adjacent pairs have a difference of 5 years.

Given the ages of the youngest and middle children, what is the age of the oldest child?

Input Specification
The input consists of two integers, each on a separate line. The first line is the age Y of the youngest child (0 ≤ Y ≤ 50). The second line is the age M of the middle child (Y ≤ M ≤ 50).

Output Specification
The output will be the age of the oldest child.

Sample Input 1
12
15

Output for Sample Input 1
18

Sample Input 2
10
10

Output for Sample Input 2
10

My solution (in Java):

import java.util.Scanner;
import java.io.File;

public class CCC_Problem_J1_Next_In_Line {
public static void main(String[] args) {

try {
Scanner file = new Scanner(new File("C:\\Users\\Mike\\Desktop\\ccc_2013\\stage_1\\test_data\\j1\\j1.1.in"));

int youngest = Integer.parseInt(file.nextLine()), middle = Integer.parseInt(file.nextLine());
System.out.println(middle + (middle - youngest));

} catch (Exception e) {
e.printStackTrace();
}
}
}

Test cases (as .in files):

Using their test cases:

50
50

And the output to that is:

50

And that is exactly the expected output

0
50

And the output to that is:

100

And that is exactly the expected output

21
37

And the output to that is:

53

And that is exactly the expected output

2
9

And the output to that is:

16

And that is exactly the expected output