import sys
input = sys.stdin.readline

def era(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(2*i, n+1, i):
            is_prime[j] = False
    
    return is_prime

is_prime = era(5*10**6+100)

for _ in range(int(input())):
    A, P = map(int, input().split())
    
    if is_prime[P]:
        print(1)
    else:
        print(-1)