IsPrime = [True for _ in range(5 * 10**6 + 1)]
IsPrime[0] = IsPrime[1] = False
for i in range(2, 5 * 10**6 + 1):
    if IsPrime[i]:
        for j in range(i + i, 5 * 10**6 + 1, i):
            IsPrime[j] = False

t = int(input())
for _ in range(t):
    a, p = map(int, input().split())
    if IsPrime[p]:
        print(1)
    else:
        print(-1)