#include <stdc++.h>                                                                                                     using namespace std;                                                                                                    int main(){
        int A,B,p;
        1<=A<=20;                                                                                                               1<=B<=20;                                                                                                               p=A*B;                                                                                                                                                                                                                                          cin<<A<<B<<endl;
        if(a<=9 && b<=9 ){                                                                                                              cout>>p>>endl;                                                                                                  }                                                                                                                       else{                                                                                                                           cout>>"-1">>endl;                                                                                               }                                                                                                                