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 math

tax8 =0.08
tax10=0.1
# price = org * (1 + tax)
# org * tax = (price - org) = X
# org = X / tax

A,B = map(int, raw_input().split())

org_a = math.ceil(A / tax8)
org_b = math.ceil(B / tax10)

#print org_a, org_b

#print math.floor(org_a * tax8),  math.floor(org_a * tax10)
#print math.floor(org_b * tax8),  math.floor(org_b * tax10)

if math.floor(org_a * tax8) == A and  math.floor(org_a * tax10) == B:
    print int(org_a)
elif math.floor(org_b * tax8) == A and math.floor(org_b * tax10) == B:
    print int(org_b)
else:
    print -1

