import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    static int profit(int b, int s, int c) {
       
        for(int i=0;i<=4000;i++){
            if((b-i+s-i)==(c-i))return i;
        }
        return -1;
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int t = in.nextInt();
        for(int a0 = 0; a0 < t; a0++){
            int b = in.nextInt();
            int s = in.nextInt();
            int c = in.nextInt();
            int result = profit(b, s, c);
            System.out.println(result);
        }
        in.close();
    }
}