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);
		float A = sc.nextFloat();
		float B = sc.nextFloat();
		int R = -1;
		float Rmemo = Math.min((float)(A/0.08), (float)(B/0.1));
		while(Rmemo*0.08 < A + 1) {
			int x = (int)Math.floor(Rmemo*0.08);
			int y = (int)Math.floor(Rmemo*0.1);
			if(x == A && y == B) {
				R = (int)Rmemo;
				break;
			}
			Rmemo++;
		}
		System.out.println(R);
	}
}