#include <bits/stdc++.h>
using namespace std;
int main() {
  int a, b;
  cout << "Pleas Enter Two Numbers : ";
  cin >> a;
  cin >> b;
  if (a >= 1 && a <= 9) {
    if (b >= 1 && b <= 9) cout << a * b;
  } else {
    cout << "-1";
  }
  return 0;
}
