Problem:
Score : 100 points

Problem Statement

Having learned the multiplication table, Takahashi can multiply two integers between 1 and 9 (inclusive) together. He cannot do any other calculation.

Given are two integers A and B.

If Takahashi can calculate A \times B, print the result; if he cannot, print -1 instead.

Constraints

1 \leq A \leq 20

1 \leq B \leq 20

All values in input are integers.

Input

Input is given from Standard Input in the following format:

A B

Output

If Takahashi can calculate A \times B, print the result; if he cannot, print -1.

Sample Input 1

2 5

Sample Output 1

10

2 \times 5 = 10.

Sample Input 2

5 10

Sample Output 2

-1

5\times 10 = 50, but Takahashi cannot do this calculation, so print -1 instead.

Sample Input 3

9 9

Sample Output 3

81

Solution in JavaScript (Node.js 12.16.1) (judge verdict: Accepted)

"use strict";
function main(input) {
    const line = input.split("\n");
    let arr = line[0].split(" ");
    const A = parseInt(arr[0]);
    const B = parseInt(arr[1]);
    console.log(A <= 9 && B <= 9 ? A * B : -1);
    return;
}
main(require('fs').readFileSync('/dev/stdin', 'utf8'));