#include<bits/stdc++.h>
using namespace std;

#define int long long

typedef long long ll;
typedef pair<int,int>pint;
typedef vector<int>vint;
typedef vector<pint>vpint;
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define ln <<endl
#define all(v) (v).begin(),(v).end()
#define rep(i,n) for(int i=0;i<(n);i++)
#define reps(i,f,n) for(int i=(f);i<(n);i++)
#define each(it,v) for(__typeof((v).begin()) it=(v).begin();it!=(v).end();it++)
template<class T,class U>void chmin(T &t,U f){if(t>f)t=f;}
template<class T,class U>void chmax(T &t,U f){if(t<f)t=f;}

int N,M;

int gcd(int a,int b){
    return b?gcd(b,a%b):a;
}

signed main(){
    stringstream ss;
    cin>>N>>M;
    int g=gcd(N,M);
    N/=g;M/=g;
    
    int hoge=M;
    while(hoge%2==0)hoge/=2;
    while(hoge%5==0)hoge/=5;
    if(hoge!=1){
        cout<<-1<<endl;
        return 0;
    }
    
    ss<<N/M;
    N=N%M*10;
    while(N){
        ss<<N/M;
        N=N%M*10;
    }
    string s=ss.str();reverse(all(s));
    rep(i,s.size()){
        if(s[i]!='0'){
            cout<<s[i]<<endl;
            return 0;
        }
    }
    return 0;
}