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 Java8 (OpenJDK 1.8.0) (judge verdict: Wrong Answer)

import java.util.Scanner;
import java.math.BigInteger;

public class Main{
    public static void main(String[] args) {
        Scanner stdIn = new Scanner(System.in);

        long a = stdIn.nextLong();
        long b = stdIn.nextLong();

        BigInteger BigA = BigInteger.valueOf(a);
        BigInteger BigB = BigInteger.valueOf(b);

        BigInteger Big25 = BigInteger.valueOf(25);
        BigInteger Big2 = BigInteger.valueOf(2);
        BigInteger Big1 = BigInteger.valueOf(1);
        BigInteger Big10 = BigInteger.valueOf(10);

        BigInteger l1 = Big25.multiply(BigA).divide(Big2);
        BigInteger r1 = Big25.multiply((BigA.add(Big1))).divide(Big2);
        BigInteger l2 = Big10.multiply(BigB);
        BigInteger r2 = Big10.multiply((BigB.add(Big1)));

        if(r1.compareTo(l2) == -1 || r2.compareTo(l1) == -1){
            System.out.println(-1);
        }else{
            System.out.println(l1.compareTo(l2) == -1 ? l2 : l1);
        }
    }
}