import fractions
def F(n):
    while n%2==0:n//=2
    while n%5==0:n//=5
    return n == 1
n,m=int(input()),int(input())
if F(fractions.Fraction(n,m).denominator):
    for x in str(format(n/m,'.14f'))[::-1]:
        if x not in['0','.'] :print(x);break
else:print(-1)