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(String[] args) {
    		Scanner sc = new Scanner(System.in);
    		 int x =sc.nextInt();
    		 int y =sc.nextInt();
    		 
    		 for(int i=1; i<=100000; i++) {
    		 if((int)(i*0.08)==x && (int)(i*0.1)==y) {
    			 System.out.println(i);
    			 return;
    		 	}
    		 }	
    			 System.out.println("-1");
        }
    }