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.*;

class Main{
public static void main(String args[]){
   Scanner sc = new Scanner(System.in);
   int a = sc.nextInt();
   int b = sc.nextInt();
   for (double price=0;price<200000;price++){
     int tax8 = (int)(price*0.08);
     int tax10 = (int)(price*0.1);
     if ((tax8 == a)&&(tax10 == b)){
        System.out.println((int)price);
        System.exit(0);
     }
   }
   System.out.println(-1);
}
}