import math
def is_prime(n):
    if n == 1: return False
    for k in range(2, int(math.sqrt(n)) + 1):
        if n % k == 0:
            return False
    return True

t = int(input())
for _ in range(t):
    a, p = map(int, input().split())
    if is_prime(p):
        print(1)
    else:
        print(-1)