import java.io.*; import java.util.*; import java.util.stream.*; public class Main { public static void main(String[] args) throws Exception { Scanner sc = new Scanner(); long n = sc.nextLong(); long m = sc.nextLong(); long gcd = getGCD(n, m); n /= gcd; m /= gcd; if (!check(m)) { System.out.println(-1); return; } long mod = n; while (mod > 0) { n = mod / m; mod %= m; mod *= 10; } while (n % 10 == 0) { n /= 10; } n %= 10; System.out.println(n); } static long getGCD(long x, long y) { if (y == 0) { return x; } else { return getGCD(y, x % y); } } static boolean check(long x) { while (x % 2 == 0) { x /= 2; } while (x % 5 == 0) { x /= 5; } return x == 1; } } class Utilities { static String arrayToLineString(Object[] arr) { return Arrays.stream(arr).map(x -> x.toString()).collect(Collectors.joining("\n")); } static String arrayToLineString(int[] arr) { return String.join("\n", Arrays.stream(arr).mapToObj(String::valueOf).toArray(String[]::new)); } } class Scanner { BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); StringTokenizer st = new StringTokenizer(""); StringBuilder sb = new StringBuilder(); public Scanner() throws Exception { } public int nextInt() throws Exception { return Integer.parseInt(next()); } public long nextLong() throws Exception { return Long.parseLong(next()); } public double nextDouble() throws Exception { return Double.parseDouble(next()); } public int[] nextIntArray() throws Exception { return Stream.of(br.readLine().split(" ")).mapToInt(Integer::parseInt).toArray(); } public String next() throws Exception { while (!st.hasMoreTokens()) { st = new StringTokenizer(br.readLine()); } return st.nextToken(); } }