P=[0 for i in range(5*10**6+1)]
P[0]=1
P[1]=1
#print(len(P))
for i in range(2,len(P)):
    if P[i]==0:
        for j in range(2,len(P)):
            if i*j>5*10**6:
                break
            else:
                P[i*j]=1
import sys
input=sys.stdin.readline
Q=int(input())
for q in range(Q):
    A,T=map(int,input().split())
    if P[T]==0:
        print(1)
    else:
        print(-1)