import java.util.Scanner;
import java.math.*;
import java.text.*;
import java.math.BigInteger;
import java.util.*;
import java.io.*;

public class Main {
	public static void main(String[] args){
	Scanner cin = new Scanner(System.in);
	int k;
    while(cin.hasNext()){ 
        BigInteger n;
        BigInteger a,b1,b2,ans,temp1,temp2;
        n = cin.nextBigInteger();
        k = cin.nextInt(); 
        temp1=BigInteger.TEN.pow(k);
        ans=BigInteger.ONE;
        
        n=n.mod(temp1);
        a=n;
        temp2 =BigInteger.ONE;
        int flag=0,flag1=0;
        for(int i=1;i<=k;i++)
        {
        	b1=a;
        	temp2=temp2.multiply(BigInteger.TEN);
        	flag1=0;
        	for(int j=1;j<=10;j++)
        	{
        		b2=b1.multiply(a).mod(temp1);
        		//System.out.println(b2);
        		//System.out.println(a);
        		//System.out.println(i);
        		//System.out.println("+++++++++");
        		if(b2.mod(temp2).equals(a.mod(temp2)))
        		{
        			if(!b1.multiply(n).mod(temp2).equals(n.mod(temp2)))
        			{
        				flag=1;
        				//System.out.println(a.mod(temp2));
        			}
        			ans=ans.multiply(BigInteger.valueOf(j));
        			a=b1;
        			flag1=1;
        			break;
        		}
        		else b1=b2;
        	}
        	if(flag1!=1) flag=1;
        	if(flag==1) break;
        	
        		 
        }
        if(flag==1) System.out.println(-1);
        else
        System.out.println(ans.toString());
    }
	}
	
}

/**************************************************************
	Problem: 2255
	User: admin
	Language: Java
	Result: Accepted
	Time:4060 ms
	Memory:42356 kb
****************************************************************/