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 Python (3.4.3) (judge verdict: Accepted)

import decimal

temp = input().split()

A, B = [int(num) for num in temp]
# print(A, B)

tax_rate_A = decimal.Decimal("0.08")
tax_rate_B = decimal.Decimal("0.10")


def calc_price_list(tax, tax_rate):
    temp = tax / tax_rate
    price_l = temp.to_integral_value(rounding=decimal.ROUND_UP)
    
    temp = (tax + 1) / tax_rate
    price_u = temp.to_integral_value(rounding=decimal.ROUND_UP)

    return list(range(int(price_l), int(price_u)))


price_A_list = calc_price_list(A, tax_rate_A)
# print(price_A_list)
price_B_list = calc_price_list(B, tax_rate_B)
# print(price_B_list)

price_set = set(price_A_list) & set(price_B_list)
# print(price_set)

if len(price_set) == 0:
    print("-1")
else:
    price_list = sorted(list(price_set))
    price = price_list[0]
    print(price)