import sys; input = sys.stdin.buffer.readline
sys.setrecursionlimit(10**7)
from collections import defaultdict
con = 10 ** 9 + 7; INF = float("inf")

def getlist():
	return list(map(int, input().split()))

num = 5 + 10 ** 6 + 1 #適当に値を入れる
L = [1 for i in range(num)]; L[0] = 0; L[1] = 0
pbit = [0] * num
plist = []
for i in range(num):
	if L[i] == 1:
		pbit[i] = 1
		plist.append(i); c = 2
		while i * c <= num - 1:
			L[i * c] = 0; c += 1

#処理内容
def main():
	T = int(input())
	for x in range(T):
		A, P = getlist()
		if pbit[P] != 1:
			print(-1)
		else:
			print(1)

if __name__ == '__main__':
	main()