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(),B=sc.nextInt();
		int Amin= A*100/8, Amax=(A+1)*100/8,Bmin= B*100/10, Bmax=(B+1)*100/10;
		if(A%2==1) {
			Amin+=1;
		}
		int ans = -1;
		for(int i=Amin;i<Amax;i++) {
			if(Bmin<=i&&Bmax>i) {
				ans = i;
				break;
			}
		}
		System.out.println(ans);
	}

}
