#!/bin/python3

import sys

q = int(input().strip())
for a0 in range(q):
    len,c = input().strip().split(' ')
    len,c = [int(len),int(c)]

    #edge case
    if len == 1 and c == 0:
        print(1)
    #too many comparisons:
    elif ((len - 1)**2 + (len - 1)) < c:
        print(-1)
    #too few comparisons
    elif c < (len - 1):
        print(-1)
    #get to work
    else:
        print("placeholder")