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

public class Solution {

     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();
            if(len ==1){
            	if(c==0){
            		System.out.println("5");
            	}
            	else{
            		System.out.println("-1");
            	}
            }
            if(c<len){
            	System.out.println("-1");
            }
            // your code goes here
            int max = (len-1)*(len-2)/2;
            if (c>max){
            	System.out.println("-1");
            }
            else if(c==max){
            	int[]ret = new int[len];
            	for(int i=0;i<len;i++){
            		ret[i]=len-i;
            	}
            }
            else{
            	int x = c-max;
            	
            }
        }
}