#!/usr/bin/env pypy3

from sys import stdin, stdout
 
def input():
    return stdin.readline().strip()

import math

class Sieve:
    def __init__(self, n=10**6+100):
        self.N = n

        s = [-1] * n
        for i in range(2, int(n**0.5)+1):
            if s[i] != -1: continue
            for j in range(i, n, i): 
                if j > i: s[j] = i
        self.s = s

        self.PRIMES = self.primes()
        # print(len(self.PRIMES))
    
    def primes(self):
        return [i for i, e in enumerate(self.s) if e == -1 and i >= 2]

    def fastfactorize(self, n):
        assert(n <= self.N)

        ret = []

        while self.s[n] != -1:
            ret += [self.s[n]]
            n = n // self.s[n]

        ret += [n]

        return ret

    def isprime(self, n):
        if n < self.N:
            return self.s[n] == -1
        for p in self.PRIMES:
            if p*p > n:
                return True
            if n % p == 0:
                return False

    def factorize(self, n):
        if n < self.N:
            return self.fastfactorize(n)
        
        for p in self.PRIMES:
            if p*p > n:
                break
            if n % p == 0:
                return [p] + self.factorize(n // p)

        return [n]

sieve = Sieve()

def ans(A, P):
    if P in [0,1]:
        return -1
    if sieve.s[P] == -1:
        return 1
    return -1
 
T = int(input())

for _ in range(T):
    AP = input().split(' ')
    A = int(AP[0])
    P = int(AP[1])
    A = int(A)
    P = int(P)

    print(ans(A, P))