import sys
input=sys.stdin.readline
def is_prime(n):
  if n==1:return False
  for i in range(2,int(n**0.5)+1):
    if n%i==0:return False
  return True
for _ in range(int(input())):
  a,p=map(int,input().split())
  if is_prime(p):print(1)
  else:print(-1)