#include<iostream>
using namespace std;
long N,M;
long gcd(long a,long b){return b?gcd(b,a%b):a;}
main()
{
	cin>>N>>M;
	long d=gcd(N,M);
	N/=d;
	M/=d;
	int c2=0,c5=0;
	while(M%2==0)c2++,M/=2;
	while(M%5==0)c5++,M/=5;
	if(M!=1)
	{
		cout<<-1<<endl;
		return 0;
	}
	while(N%10==0)N/=10;
	N%=10;
	for(int i=c2;i<c5;i++)N=N*2%10;
	for(int i=c5;i<c2;i++)N=N*5%10;
	cout<<N<<endl;
}