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: Accepted)

import java.awt.Event;
import java.awt.geom.Point2D;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.nio.channels.FileChannel;
import java.sql.Timestamp;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.Scanner;
import java.util.TreeSet;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.stream.IntStream;

public class Main {
	Scanner sc = new Scanner(System.in);
	public static void main(String[] args){
		new Main();
	}
	public Main(){
//		new TestA().doIt();
//		new TestB().doIt();
		new TestC().doIt();
	}
	class TestA{
		void doIt() {
			String str = sc.next();
			if(str.equals("AAA") || str.equals("BBB")) {
				System.out.println("No");
			}else {
				System.out.println("Yes");
			}
		}
	}
	class TestB{
		void doIt() {
			long N = Long.parseLong(sc.next());
			long A = Long.parseLong(sc.next());
			long B = Long.parseLong(sc.next());
			long Loop = N / (A + B);
			N = N % (A + B);
			
			long Acount = Loop * A;
			if(N < A)Acount += N;
			else if(N >= A)Acount += A;
			
			System.out.println(Acount);
		}
	}
	class TestC{
		void doIt() {
			int A = Integer.parseInt(sc.next());
			int B = Integer.parseInt(sc.next());
			int num = 0;
			while(true) {
				int numA = (int)(num * 0.08);
				int numB = (int)(num * 0.10);
				if(numA == A && numB == B)break;
				if(numA > A) {
					num = -1;
					break;
				}
				num++;
			}
			System.out.println(num);
		}
	}
}