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 A =sc.nextInt();
		 int B =sc.nextInt();
		 //i*0.08とi*0.1が等しくなるまで繰り返す
		 for(int i=1; i<=100000; i++) {
		 if((int)(i*0.08)==A && (int)(i*0.1)==B) {
			 System.out.println(i);
			 return;
		 	}
		 }	//なかった場合は-1を表示
			 System.out.println("-1");
    }
}