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;
class Program
{
	static void Main(string[] args)
	{
		// スペース区切りの整数の入力
		string[] input = Console.ReadLine().Split(' ');
		int a = int.Parse(input[0]);
		int b = int.Parse(input[1]);
   
        int ans = calcNum(a, b);  
      
		//出力
		Console.WriteLine(ans);
	}
  
    static int calcNum(int A, int B)
    {
        int rNum = 0;

        // Aの値を確認(四捨五入)
        // Aが2の場合minAは25、maxAは37
        // Aが8の場合minAは100、maxAは112
        // Aが19の場合minAは238、maxAは249
        int minA = (int)Math.Floor(A / 0.08 + 0.5);
        int maxA = (int)Math.Floor(((A+1) / 0.08) + 0.5) - 1;

        // Bの値を確認(四捨五入)
        // Bが2の場合minAは20、maxAは37
        // Bが10の場合minBは100、maxBは109
        // Bが99の場合minBは990、maxBは999
        int minB = (int)Math.Floor(B / 0.1 + 0.5);
        int maxB = (int)Math.Floor(((B+1) / 0.1) + 0.5) - 1;

        // 最小値の範囲で比較
        if(minA <= minB)
        {
            if(minB <= maxA)
            {
                rNum = minB;
            }
            else
            {
                rNum = -1;
            }
        }
        else
        {
            if(minA <= maxB)
            {
                rNum = minA;
            }
            else
            {
                rNum = -1;
            }
        }

        return rNum;
    }

}