#!/usr/bin/ruby
require 'rational'
require 'prime'
n=gets.to_i
m=gets.to_i
g=n.gcd(m)
n/=g
m/=g
n/=10 while n%10==0
m/=10 while m%10==0
div=m.prime_division
if div.any?{|n,p|n!=2&&n!=5}
	p -1
	exit
end
div=Hash[*div.flatten(1)]
n%=10
(div[2]||0).times{|i|
	n*=5
	n = n%10==0 ? n/10 : n%10
}
(div[5]||0).times{|i|
	n*=2
	n = n%10==0 ? n/10 : n%10
}
p n