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