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.io.*;
import java.util.*;
import java.math.*;
     
public class Main{
	public static void main(String[] args) throws Exception {
	IO io = new IO();
	PrintWriter out = new PrintWriter(System.out);
	Solver sr = new Solver();
	sr.solve(io,out);
	out.flush();
	out.close();
    	}

	static class Solver
	{
	    void solve(IO io, PrintWriter out)
	    {
          int x = io.nextInt();
          int y = io.nextInt();
          
          long tmp = (long)Math.floor((x*100)/8);
          long min = Long.MAX_VALUE;
          if((long)Math.floor(tmp*0.1)==y)
            min = Math.min(min,tmp);
          tmp = (long)Math.floor((y*10));
          if((long)Math.floor((tmp*8)/100)==x)
            min = Math.min(min,tmp);
          if(min!=Long.MAX_VALUE)
            out.print(min);
          else
            out.print("-1");
	    }
    	
	}
	//Special thanks to Petr (on codeforces) who inspired me to implement IO class!
	static class IO
	{
    	BufferedReader reader;
        StringTokenizer tokenizer;
    	public IO() {
                reader = new BufferedReader(new InputStreamReader(System.in));
                tokenizer = null;
            }
     
        public String next() {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }
        public String nextLine() {
            String s="";
            try {
                    s=reader.readLine();
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            return s;
        }
        public int nextInt() {
            return Integer.parseInt(next());
        }
    
        public long nextLong() {
            return Long.parseLong(next());
        }
    	double nextDouble()
    	{
    		return Double.parseDouble(next());
    	}
	}
}