from math import gcd

T = int(input())
assert(1 <= T <= 10 ** 5)
for _ in range(T):
	N, M = map(int, input().split())
	assert(1 <= N <= 10 ** 18)
	assert(1 <= M <= 10 ** 18)
	g = gcd(gcd(N, M), 10 ** 9)
	N //= g
	M //= g
	m = 10 ** 9 // g
	if N % m == 0 or gcd(N, m) > 1:
		print(-1)
	else:
		a = -M * pow(N, -1, m) % m
		print(a if a > 0 else 10 ** 9)