import sys

# sys.setrecursionlimit(200005)
int1 = lambda x: int(x)-1
p2D = lambda x: print(*x, sep="\n")
def II(): return int(sys.stdin.buffer.readline())
def LI(): return list(map(int, sys.stdin.buffer.readline().split()))
def LI1(): return list(map(int1, sys.stdin.buffer.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def LLI1(rows_number): return [LI1() for _ in range(rows_number)]
def BI(): return sys.stdin.buffer.readline().rstrip()
def SI(): return sys.stdin.buffer.readline().rstrip().decode()
# dij = [(0, 1), (-1, 0), (0, -1), (1, 0)]
dij = [(0, 1), (-1, 0), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)]
inf = 10**16
md = 998244353
# md = 10**9+7

from random import randrange

def is_prime(n):
    # K...信頼度
    K = 100
    if n == 2: return True
    if n == 1 or n & 1 == 0: return False
    d = (n-1) >> 1
    while d & 1 == 0: d >>= 1
    for k in range(K):
        a = randrange(1, n)
        t = d
        y = pow(a, t, n)
        while t != n-1 and y != 1 and y != n-1:
            y = (y*y)%n
            t <<= 1
        if y != n-1 and t & 1 == 0: return False
    return True

def solve():
    a,p=LI()
    if is_prime(p):print(1)
    else:print(-1)

for _ in range(II()):
    solve()