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 {
	static Scanner sc = new Scanner(System.in);

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		int a = Integer.parseInt(sc.next());
		int b = Integer.parseInt(sc.next());

		for (int p = 1; p <= 1000; ++p) {
			int tax8 = p * 8 / 100;
			if (tax8 != a) {
				continue;
			}

			int tax10 = p * 10 / 100;
			if (tax10 != b) {
				continue;
			}

			System.out.println(p);
			return;
		}

		System.out.println(-1);
	}

}
