Problem:
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.

Solution in C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;

namespace C
{
	class Program
	{
		static void Main(string[] args)
		{
			string[] tmp = Console.ReadLine().Split(' ');
			int a = int.Parse(tmp[0]);
			int b = int.Parse(tmp[1]);

			// (a+1)/0.08 ~ a/0.08と(b+1)/0.1~b/0.1が被っているとき、その被っている領域の最小を吐く
			if ((int)((a+1)/0.08)-((a+1)/0.08%1>0?0:1) >= (int)b/0.1 && (b+1)/0.1-1 >= (int)a/0.08)
			{
				Console.WriteLine(Math.Max((int)(a / 0.08), (int)(b / 0.1)));
			}
			else {
				Console.WriteLine(-1);
			}
		}
	}
}