import std.conv, std.functional, std.range, std.stdio, std.string;
import std.algorithm, std.array, std.bigint, std.complex, std.container, std.math, std.numeric, std.regex, std.typecons;
import core.bitop;

class EOFException : Throwable { this() { super("EOF"); } }
string[] tokens;
string readToken() { for (; tokens.empty; ) { if (stdin.eof) { throw new EOFException; } tokens = readln.split; } auto token = tokens.front; tokens.popFront; return token; }
int readInt() { return readToken.to!int; }
long readLong() { return readToken.to!long; }
real readReal() { return readToken.to!real; }

bool chmin(T)(ref T t, in T f) { if (t > f) { t = f; return true; } else { return false; } }
bool chmax(T)(ref T t, in T f) { if (t < f) { t = f; return true; } else { return false; } }

int binarySearch(alias pred, T)(in T[] as) { int lo = -1, hi = cast(int)(as.length); for (; lo + 1 < hi; ) { const mid = (lo + hi) >> 1; (unaryFun!pred(as[mid]) ? hi : lo) = mid; } return hi; }
int lowerBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a >= val)); }
int upperBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a > val)); }


BigInt N, M;

void main() {
  try {
    for (; ; ) {
      N = BigInt(readToken());
      M = BigInt(readToken());
      
      BigInt m = M;
      int e2, e5;
      for (; m % 2 == 0; m /= 2) ++e2;
      for (; m % 5 == 0; m /= 5) ++e5;
      if (m > 1) {
        writeln(-1);
      } else {
        BigInt x = N;
        if (e2 < e5) {
          foreach (_; 0 .. e5 - e2) {
            x *= 2;
          }
        } else {
          foreach (_; 0 .. e2 - e5) {
            x *= 5;
          }
        }
        for (; x % 10 == 0; x /= 10) {}
        writeln(x % 10);
      }
    }
  } catch (EOFException e) {
  }
}