def get_sieve_of_eratosthenes_new(n):
    import math
    if not isinstance(n, int):
        raise TypeError('n is int type.')
    if n < 2:
        raise ValueError('n is more than 2')
    prime = []
    limit = math.sqrt(n)
    data = [i + 1 for i in range(1, n)]
    while True:
        p = data[0]
        if limit <= p:
            return prime + data
        prime.append(p)
        data = [e for e in data if e % p != 0]

prime=set(get_sieve_of_eratosthenes_new(5000000))


import sys

input=sys.stdin.readline
for _ in range(int(input())):
    a,p=map(int,input().split())
    if p in prime:
        print(1)
    else:
        print(-1)