from math import gcd
for _ in range(int(input())):
	N, M = map(int, input().split())
	N %= 10 ** 9
	M %= 10 ** 9
	if N == 0:
		if M == 0:
			print(1)
		else:
			print(-1)
	else:
		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)