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: Accepted)

using System;
using System.IO;
using System.Linq;
using System.Collections.Generic;
using System.Numerics;

namespace abc185
{
    class Program
    {
        static void Main(string[] args)
        {
            if (File.Exists("input.txt"))
            {
                Console.SetIn(new StreamReader("input.txt"));
            }
			solve_abc185C();
        }

        public static void solve_abc185C()
        {
            int[] ab = Array.ConvertAll(Console.ReadLine().Split(), int.Parse);
            int a = ab[0];
            int b = ab[1];
            bool ok = false;
            int x = 0;
            for (int i = 1; i <= 10000; i++)
            {
                if ((i * 8) / 100 == a && (i * 10) / 100 == b)
                {
                    ok = true;
                    x = i;
                    break;
                }
            }
            if (ok)
            {
                Console.WriteLine(x);
            }
            else
            {
                Console.WriteLine(-1);
            }
        }

        public static void solve_abc185B()
        {
            long[] nab = Array.ConvertAll(Console.ReadLine().Split(), long.Parse);
            long n = nab[0];
            long a = nab[1];
            long b = nab[2];
            long x = n / (a + b);
            long xr = n % (a + b);
            Console.WriteLine(a > 0 ? x * a + Math.Min(xr, a) : 0);
        }

        public static void solve_abc185A()
        {
            string s = Console.ReadLine();

            if (s.Contains('A') && s.Contains('B'))
            {
                Console.WriteLine("Yes");
            }
            else
            {
                Console.WriteLine("No");
            }
        }
    }
}