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 sc = new Scanner(System.in);
    	int A= sc.nextInt();
    	int B = sc.nextInt();
    	
    	for(int i = 1 ; i <= 1000 ; i++){
      		if((int)(i*0.08) == A && (int)(i*0.1) == B){
        		System.out.println(i);
        		return;
      		}
    	}
 
    	System.out.println(-1);
    
  }
}