import sys
input = sys.stdin.readline

def calc(A,P):
    ANS=1
    for i in range(1,P+1):
        ANS*=i
    return pow(A,ANS,P)

import math
x=5*10**6+10
L=math.floor(math.sqrt(x)) # 平方根を求める

Primelist=[i for i in range(x+1)]
Primelist[1]=0 # 1は素数でないので0にする.
 
for i in Primelist:
    if i>L:
        break
    if i==0:
        continue
    for j in range(2*i,x+1,i):
        Primelist[j]=0

Primes=[Primelist[j] for j in range(x+1) if Primelist[j]!=0]
S=set(Primes)

T=int(input())
for tests in range(T):
    A,P=map(int,input().split())

    if P in S:
        print(1)
    else:
        print(-1)