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-----
2 5

-----Sample Output-----
10

2 \times 5 = 10.