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) {
		// TODO 自動生成されたメソッド・スタブ
		Scanner sc = new Scanner(System.in);
	    int a = sc.nextInt();
	    int b = sc.nextInt();
	    int price = 10*b;
	    boolean flag = false;
	    for(int i = 0; i < 10; i++) {
	    	if((int)((price+i)*0.08) == a) {
	    		System.out.println(price+i);
	    		flag = true;
	    		break;
	    	}
	    }
	    if(flag == false) {
	    	System.out.println(-1);
	    }

	}

}