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.*;
    public class Main {
     
    	public static void main(String[] args) {
    		Scanner scan = new Scanner(System.in);
    		int a=Integer.parseInt(scan.next());
    		int b=Integer.parseInt(scan.next());
    		
    		for (int i=1;i<1010;++i) {
    			if ((int)(i*0.08)==a && (int)(i*0.1)==b) {
    				System.out.print(i);
    				System.exit(0);
    				break;
    			}
    		}
    		System.out.print(-1);
    		
    		
    }	
    }
// end 