#coding: utf-8
##yuki_25
import sys

def gcd(x,y):
 while y:
  x,y=y,x%y
 return x

def prime_count(n):
 count5=0
 count2=0
 while n%10==0:
  n=n/10
 while n%5==0:
  n=n/5
  count5+=1
 while n%2==0:
  n=n/2
  count2+=1
 if n!=1:
  return False
 return count5,count2


 
n=int(raw_input())
m=int(raw_input())

d=gcd(n,m)
n=n/d
m=m/d
if prime_count(m)==False:
 print -1
 sys.exit()
if m==1:
 while n%10==0:
  n=n/10
 print n%10
 sys.exit()
c5,c2=prime_count(m)
while n%10==0:
 n=n/10
n%10
while c2<c5:
 n=(n*2)%10
 c2+=1
while c2>c5:
 n=(n*5)%10
 c5+=1

print n