import fractions
from decimal import *
def F(n):
    while n%2==0:n//=2
    while n%5==0:n//=5
    return n == 1
getcontext().prec=1000
n,m=Decimal(input()),Decimal(input())
x=str(n/m)
if 'E' in x:x=x[:x.index('E')]
if F(fractions.Fraction(int(n),int(m)).denominator):
    for x in x[::-1]:
        if x not in['0','.'] :print(x);break
else:print(-1)