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;
import java.util.Arrays;

public class Main{
public static void main(String[] args){
Scanner scan=new Scanner(System.in);
int a=scan.nextInt();
int b=scan.nextInt();

int i=1;
for(i=1;i<=2000;i++){
  if((i*8/100==a)&&(i*10/100==b)){
    break;
  }
}
  
  
if(i==2001){
System.out.println(-1);
}else{
  System.out.println(i);
}

}
}