#!/bin/python

import sys


q = int(raw_input().strip())
for a0 in xrange(q):
    length,c = raw_input().strip().split(' ')
    length,c = [int(length),int(c)]
    # your code goes here
    if c == 1 and length > 0:
        print '-1'
    elif c > length * (length - 1) / 2 or c < length - 1:
        print '-1'
    else:
        print 'idk :('