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 sys
import math

f = sys.stdin.readline()
xx = f.split(' ')
x = [int(str) for str in xx]

a = x[0]
aa = a+1
b = x[1]
bb = b+1


x = int(a / 0.08)
xx = int(aa / 0.08)
y = int(b / 0.1)
yy = int(bb / 0.1)


if ( x > y ):
	min = x
	if( x * 0.08 < a):
		min = x + 1
	if( min >= yy):
		print "-1"
	else:
		print min
else:
	min = y
	if( min >= xx):
		print "-1"
	else:
		print min

sys.stdout.flush()