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 sca = new Scanner(System.in);
	int a = sca.nextInt(); // 8％
	int b = sca.nextInt(); // 10％
	int ans = 0;

	for(int i = 1 ; i <= 1251; i++) {
		if((int)(i * 0.08) == a && (int)(i * 0.1) == b) {
			ans = i;
			break;
		}
		if(i == 1251) {
			ans = -1;
		}
	}

	System.out.println(ans);

	// 後始末
	sca.close();
	}
}