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`.

Examples

Input

2 2


Output

25


Input

8 10


Output

100


Input

19 99


Output

-1
import java.util.Scanner;

public class Main {
    public static void main(final String[] args) {
    	Scanner scanner = new Scanner(System.in);
    	int a = scanner.nextInt(), b = scanner.nextInt();
    	boolean flag = false;
    	for(int i=1;i<=100000;i++) {
    		if (Math.floor(1.* i *.08) == a && b == Math.floor(.1 * i)) {
    			System.out.println(i);
    			flag = true;
    			break;
    		}
    	}
    	if (!flag) {
    		System.out.println(-1);
    	}
    	}
    }
