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;
using System.Collections.Generic;
using static System.Console;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace _158_A
{
    class Program
    {
        static void Main(string[] args)
        {
            string input = ReadLine();
            string[] array = input.Split(' ');
            int[] n = new int[array.Length];
            for (int i = 0; i < array.Length; i++)
            {
                n[i] = int.Parse(array[i]);
            }
               
            int result1 = n[0] * 100 / 8;
            int result2 = n[1] * 10 / 1;
            int result3 = 0;
            int a = result2/100*108;
            int c = result1/100*110;
            if (result1 <= result2)
            {
               
                if (a-result2 == n[0])
                {
                    result3 = result2;
                }
                else {
                    result3 = -1;                
                }

            }
            else {
                if (result1 >= result2) {
                    if (c-result1 == n[1])
                    {
                        if (result3 != -1)
                        {
                            result3 = result1;
                        }
                    }
                    else {
                        result3 = -1;                     
                    }
                }
            }

            WriteLine("{0}", result3);

            ReadKey();
        }
    }
}