import java.util.Scanner;

public class Solution
{
    public static void main(String[] ARGS)
    {
        Scanner kb = new Scanner(System.in);
        int numCases = kb.nextInt();

        for (int i = 0; i < numCases; i++)
        {
            int NumHouses = kb.nextInt();
            int NumVisit = kb.nextInt();

            if(NumVisit > (NumHouses / 2))
            {
                System.out.println("0");
            }
            else
            {
                System.out.println (NumHouses + NumVisit);
            }
        }
    }
}