t = int(input())

for _ in range(t):
    a, b = map(int, input().split())
    if a > b:
        print(-1)
        continue
    res = float('inf')
    x = 0
    while x * x <= b:
        if (b + x) % (a + x) == 0:
            res = min(res, x)
        x += 1
    k = 2
    while b - k * a >= 0 and (k - 1) * (k - 1) <= b:
        if (b - k * a) % (k - 1) == 0:
            res = min(res, (b - k * a) // (k - 1))
        k += 1
    if res == float('inf'):
        res = -1
    print(res)