import math
T=int(input())

for _ in range(T):
    N,M=map(int, input().split())
    p=10**9
    g = math.gcd(N,M,10**9)
    N%=p
    M%=p
    if N==0 and M==0:
        print(1)
        continue
    elif N==0:
        print(-1)
        continue
    N//=g
    M//=g
    t=10**9//g
    if N%t==0 or math.gcd(N,t)>1:
        print(-1)
    else:
        a = -M*pow(N,-1,t)%t
        if a==0:
            print(10**9)
            continue
        print(a)