import sys
input = sys.stdin.readline

def p(x,m):
    ANS=0
    while x%m==0:
        ANS+=1
        x//=m
    return ANS

T=int(input())
for tests in range(T):
    N,M=map(int,input().split())

    N2=p(N,2)
    N5=p(N,5)

    M2=p(M,2)
    M5=p(M,5)

    if min(N2,9)<=M2 and min(N5,9)<=M5:
        pass
    else:
        print(-1)
        continue

    d=(2**min(N2,9))*(5**min(N5,9))
    

    N//=d
    M//=d

    mod=10**9

    mod//=d

    if mod==1:
        print(1)
        continue

    k=-M*pow(N,-1,mod)%mod

    if k==0:
        print(min(mod,M)//N)
    else:
        print(k)