#include <bits/stdc++.h>
int main(void) {
  int a, b, c;
  printf("please input two integers between 1 and 9(inclusive) together\n");
  scanf("%d %d", &a, &b);
  if (a < 1 || a > 9 || b < 1 || b > 9) {
    printf("-1\n");
  } else {
    c = a * b;
    printf("%d", c);
  }
}
