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 is_prime


t = int(input())
pr = primes(5 * 10 ** 6)
for _ in range(t):
    a, p = map(int, input().split())
    if pr[p]:
        print(1)
    else:
        print(-1)