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

namespace ABC158
{
    class Program
    {
        static void Main(string[] args)
        {
            c();
            //b();
        }

        public static void b()
        {
            long[] nab = Console.ReadLine().Split(' ').Select(long.Parse).ToArray();
            long n = nab[0], a = nab[1], b = nab[2];
            long sum = 0;
            long aa = n % (a + b);
            long bb = n / (a + b);
            long sum1 = 0;
            for(long i = 0; i < aa; i++)
            {
                sum1++;
            }
            sum = bb * a + sum1;
            Console.WriteLine(sum);
        }

        public static void c()
        {
            long[] ab = Console.ReadLine().Split(' ').Select(long.Parse).ToArray();
            long a = ab[0], b = ab[1];
            double aa = 0, bb = 0;
            long ans = 0;
            for (long i = 1; i < 1300; i++)
            {
                aa = Math.Floor(i * 0.08);
                for (long j = 1; j <= i; j++)
                {
                    bb = Math.Floor(j * 0.1);
                    if (i == j && aa == a && bb == b)
                    {
                        Console.WriteLine(j);
                        return;
                    }
                    //Console.WriteLine("aa == {0}  bb == {1} j == {2}", aa, bb, j);
                }
            }
             Console.WriteLine(-1);
        }
    }
}