Untitled

#include <bits/stdc++.h>
#define maxn 100000

using namespace std;

int d, k, a[maxn];
int main(){

    while ( cin >> d >> k )
    {
        if ( k == 1 ) cout << d << endl;
        else
        {
            int so = 0; int ktra = 0; int length = 1; a[1] = d; int recall = 0;
            for ( int i = 1; i <= 101; i++)
            {
                so = a[length] * k + recall;
                a[length + 1] = so % 10;
                recall = so/10;
                if ( recall == 0 && a[length + 1] == d && a[length] > 0 ) ktra = 1;
                if ( ktra == 1 )
                {
                    for ( int i = length; i >= 1; i--)
                        cout << a[i];
                    cout << endl;
                    break;
                }
                length = length + 1;
            }
            if ( ktra == 0 ) cout << -1 << endl;
        }
    }


}