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 inp = new Scanner(System.in);
    int a = inp.nextInt();
    int b = inp.nextInt();
    int f=-1;
    for( int i=0; i<100000; i++){
      int t1 = (i*8)/100;
      int t2 = (i*10)/100;
      if(t1==a && t2==b){
        f=i;
        break;
      }
    }
    System.out.println(f);

  }
}