Find the price of a product before tax such that, when the consumption tax rate is 8 percent and 10 percent, the amount of consumption tax levied on it is A yen and B yen, respectively. (Yen is the currency of Japan.)
Here, the price before tax must be a positive integer, and the amount of consumption tax is rounded down to the nearest integer.
If multiple prices satisfy the condition, print the lowest such price; if no price satisfies the condition, print -1.

-----Constraints-----
- $1 \leq A \leq B \leq 100$
- A and B are integers.

-----Input-----
Input is given from Standard Input in the following format:
A B

-----Output-----
If there is a price that satisfies the condition, print an integer representing the lowest such price; otherwise, print -1.

-----Sample Input-----
2 2

-----Sample Output-----
25

If the price of a product before tax is 25 yen, the amount of consumption tax levied on it is:
- When the consumption tax rate is 8 percent: $\lfloor 25 \times 0.08 \rfloor = \lfloor 2 \rfloor = 2$ yen.
- When the consumption tax rate is 10 percent: $\lfloor 25 \times 0.1 \rfloor = \lfloor 2.5 \rfloor = 2$ yen.
Thus, the price of 25 yen satisfies the condition. There are other possible prices, such as 26 yen, but print the minimum such price, 25.

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