mod = 1000000007
eps = 10**-9


def main():
    import sys
    input = sys.stdin.buffer.readline

    N0 = 5*10**6
    is_prime = [1] * (N0+1)
    is_prime[0] = is_prime[1] = 0
    for i in range(2, N0+1):
        if is_prime[i] == 0:
            continue
        for j in range(2, N0+1):
            if i*j > N0:
                break
            is_prime[i*j] = 0

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


if __name__ == '__main__':
    main()