#include <cstdio>
#include <cstdlib>
#include <iostream>
#include <string>
#include <cmath>
#include <algorithm>
#include <vector>
#include <queue>
#include <stack>
#include <map>
#include <set>
#include <cstring>

typedef long long ll;
using namespace std;

#define mod 1000003
#define INF 1000000000
#define LLINF 2000000000000000000LL

#define SIZE 10000

int main(){
    ll n,m,ans;
    set<ll> ss;
    
    scanf("%lld%lld",&n,&m);
    
    while(1){
        if(n%m==0){
            ans=n/m;
            
            while(ans%10==0) ans/=10;
            
            printf("%lld\n",ans);
            return 0;
        }
        
        n%=m;
        
        if(ss.find(n)!=ss.end()){
            puts("-1");
            return 0;
        }
        
        ss.insert(n);
        n*=10;
    }
    
    return 0;
}