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
×
B
, print the result; if he cannot, print -1 instead.

Constraints
1
≤
A
≤
20
1
≤
B
≤
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
×
B
, print the result; if he cannot, print -1.

Sample Input 1 
Copy
2 5
Sample Output 1 
Copy
10
2
×
5
=
10
.

Sample Input 2 
Copy
5 10
Sample Output 2 
Copy
-1
5
×
10
=
50
, but Takahashi cannot do this calculation, so print -1 instead.

