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 System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Atcoder
{
    class Program
    {
        static void Main(string[] args)
        {
            var arg = Console.ReadLine().Split(' ');
            var A = arg[0].ToDecimal();
            var B = arg[1].ToDecimal();
            var ans1 = (-1).ToDecimal();
            for (int i = 0; i < 10; i++)
            {
                var isBreak = false;
                var x = (A + i * (0.1).ToDecimal())/(0.08).ToDecimal();
                for (int j = 0; j < 10; j++)
                {
                    var y = (B + j * (0.1).ToDecimal()) / (0.1).ToDecimal();
                    if (x == y)
                    {
                        ans1 = x;
                        isBreak = true;
                        break;
                    }
                }
                if (isBreak) break;
            }

            var ans2 = (-1).ToDecimal();
            for(int i = 0; i < 10; i++)
            {
                var y = (B + i * (0.1).ToDecimal()) / (0.1).ToDecimal();
                var isBreak = false;
                for (int j = 0; j < 10; j++)
                {
                    var x = (A + j * (0.1).ToDecimal()) / (0.08).ToDecimal();
                    if (x == y)
                    {
                        ans2 = x;
                        isBreak = true;
                        break;
                    }
                }
                if (isBreak) break;
            }
            Console.WriteLine(Math.Min(ans1, ans2));
        }
    }

    public static class Extentions
    {
        public static int ToInt(this object obj)
        {
            return int.Parse(obj.ToString());
        }

        public static decimal ToDecimal(this object obj)
        {
            return decimal.Parse(obj.ToString());
        }
    }
}