101582: [AtCoder]ABC158 C - Tax Increase

Memory Limit:256 MB Time Limit:2 S
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Description

Score : $300$ points

Problem Statement

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 1

2 2

Sample Output 1

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, $25$.


Sample Input 2

8 10

Sample Output 2

100

If the price of a product before tax is $100$ yen, the amount of consumption tax levied on it is:

  • When the consumption tax rate is $8$ percent: $\lfloor 100 \times 0.08 \rfloor = 8$ yen.
  • When the consumption tax rate is $10$ percent: $\lfloor 100 \times 0.1 \rfloor = 10$ yen.

Sample Input 3

19 99

Sample Output 3

-1

There is no price before tax satisfying this condition, so print -1.

Input

题意翻译

* 一件商品税率为$8$%时消费税为$A$元,$10$%时为$B$元$。$ * 给出$A、B$,输出满足条件的商品免税价格中最小的一个;若不存在,输出$-1。$ * $A、B$均为整数且$1≤A≤B≤100$($A$、$B$均为以商品免税价计算的税率向下取整后的整数)

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