from math import gcd, lcm

MOD = 10**9

def inverse(n, d, MOD):
    return n * pow(d, -1, MOD) % MOD

for _ in range(int(input())):
    N, M = map(int, input().split())

    X = (-M)%MOD
    if X == 0:
        print(lcm(N, MOD)//N)
        continue

    GCD = gcd(N, MOD)
    if X%GCD != 0:
        print(-1)
        continue

    GCD = gcd(N, MOD, X)
    n = N//GCD
    m = MOD//GCD
    x = X//GCD

    print(inverse(x, n, m))