import sys
from collections import deque, Counter
input = lambda: sys.stdin.readline().rstrip()
ii = lambda: int(input())
mi = lambda: map(int, input().split())
li = lambda: list(mi())
inf = 2 ** 63 - 1
mod = 998244353
maxi = 10 ** 7
prime = [True] * (maxi)
prime[0] = prime[1] = False

for i in range(2, maxi):
    if prime[i]:
        for j in range(2 * i, maxi, i):
            prime[j] = False

for _ in range(ii()):
    a, p = mi()
    if prime[p]:
        print(1)
    else:
        print(-1)