import sys

input = sys.stdin.readline


def primes(n):
    is_prime = [True] * (n + 1)
    is_prime[0] = False
    is_prime[1] = False
    for i in range(2, int(n ** 0.5) + 1):
        if not is_prime[i]:
            continue
        for j in range(i * 2, n + 1, i):
            is_prime[j] = False
    return (i for i in range(n + 1) if is_prime[i])


PR = set(primes(5 * 10 ** 6))
T = int(input())
for _ in range(T):
    A, P = map(int, input().split())
    print(1 if P in PR else -1)