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

public class Solution {

    public static void main(String[] args) {
        
        Scanner in = new Scanner(System.in);
        int q = in.nextInt();
        for (int a0 = 0; a0 < q; a0++)
        {
            int len = in.nextInt();
            int c = in.nextInt();
            // your code goes here

            if (len == 1)
                System.out.println(1);
            else
            {
                int sum = (len * (len + 1)) / 2;
                if(sum < c)
                    System.out.println(-1);
                else
                    System.out.println(0);
            }
        }
    
    }
}