Score : 100 points
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.
Input is given from Standard Input in the following format:
A B
If Takahashi can calculate A \times B, print the result; if he cannot, print -1
.
2 5
10
2 \times 5 = 10.
5 10
-1
5\times 10 = 50, but Takahashi cannot do this calculation, so print -1
instead.
9 9
81