#include<stdio.h>

int main{
    int A, B, C;
    scanf{"%d, %d", A, B};

    if (A < 1 || 10 < A || B < 1 || 10 < B ){
        C = -1;
    } else {
        C = A * B
    }
    printf("%d", C);
    return 0;
}