#include <bits/stdc++.h>
int main() {
  int a, b, c;
  printf("please input integer:");
  scanf("%d %d", &a, &b);
  if (a > 9) printf("c=-1");
  if (b > 9)
    printf("c=-1");
  else
    c = a * b;
  printf("%d\n", c);
}
