import sys

# sys.setrecursionlimit(1000006)
# sys.set_int_max_str_digits(200005)
int1 = lambda x: int(x)-1
pDB = lambda *x: print(*x, end="\n", file=sys.stderr)
p2D = lambda x: print(*x, sep="\n", end="\n\n", file=sys.stderr)
def II(): return int(sys.stdin.readline())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def LI1(): return list(map(int1, sys.stdin.readline().split()))
def LLI1(rows_number): return [LI1() for _ in range(rows_number)]
def SI(): return sys.stdin.readline().rstrip()

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 = -1-(-1 << 31)
inf = -1-(-1 << 62)

# md = 10**9+7
md = 998244353

def factors(a):
    if a<=0:return [0]
    dd0,dd1=[],[]
    for d in range(1,round(a**0.5)+1):
        if a%d:continue
        dd0.append(d)
        dd1.append(a//d)
    if dd0[-1]==dd1[-1]:dd1.pop()
    return dd0+dd1[::-1]

def solve():
    b,a=LI()
    if a%b==0:
        print(0)
        return
    ans=inf
    for k in factors(a-b):
        r=a-b*(k+1)
        if r<0:break
        if r%k==0:ans=min(ans,r//k)
    if ans==inf:ans=-1
    print(ans)

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