Problem:
Score : 300 points

Problem Statement

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.

Sample Input 1

2 2

Sample Output 1

25

If the price of a product before tax is 25 yen, the amount of consumption tax levied on it is:

When the consumption tax rate is 8 percent: \lfloor 25 \times 0.08 \rfloor = \lfloor 2 \rfloor = 2 yen.

When the consumption tax rate is 10 percent: \lfloor 25 \times 0.1 \rfloor = \lfloor 2.5 \rfloor = 2 yen.

Thus, the price of 25 yen satisfies the condition. There are other possible prices, such as 26 yen, but print the minimum such price, 25.

Sample Input 2

8 10

Sample Output 2

100

If the price of a product before tax is 100 yen, the amount of consumption tax levied on it is:

When the consumption tax rate is 8 percent: \lfloor 100 \times 0.08 \rfloor = 8 yen.

When the consumption tax rate is 10 percent: \lfloor 100 \times 0.1 \rfloor = 10 yen.

Sample Input 3

19 99

Sample Output 3

-1

There is no price before tax satisfying this condition, so print -1.

Solution in Ruby (2.3.3) (judge verdict: Accepted)

A, B = gets.chomp.split.map(&:to_i)

lowestPriceForA = (A/0.08).ceil

if ((A+1)/0.08) == ((A+1)/0.08).floor then
    highestPriceForA = ((A+1)/0.08) - 1
else
    highestPriceForA = ((A+1)/0.08).floor
end

priceRangeA = []
for i in lowestPriceForA..highestPriceForA do
    priceRangeA.push(i)
end
# p priceRangeA

lowestPriceForB = (B/0.1).ceil

if ((B+1)/0.1) == ((B+1)/0.1).floor then
    highestPriceForB = ((B+1)/0.1) - 1
else
    highestPriceForB = ((B+1)/0.1).floor
end

priceRangeB = []
for i in lowestPriceForB..highestPriceForB do
    priceRangeB.push(i)
end
# p priceRangeB

mary = priceRangeA & priceRangeB
# p mary
if mary.empty? then
    puts (-1).to_s
else
    puts mary[0]
end