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: Wrong Answer)

a, b = map(int, input().split())

a1 = int(a * 100 / 8)
b1 = b * 10
c = 0
a2 = a1 + 25
b2 = b1 + 25

if a2 == b2:
    print(a2 - 25)
if abs(a2 - b2) > 25:
    print(-1)
elif a2 > b2:
    for i in range(b2, a2 + 1):
        if int(i * 0.08) == a1 and int(i * 0.1) == int(b1):
            print(i)
            break
        else:
            c = c + 1
    if c == (a2 - b2 + 1):
        print(-1)
elif a2 < b2:
    for i in range(a2, b2 + 1):
        if int(i * 0.08) == a1 and int(i * 0.1) == int(b1):
            print(i)
            break
        else:
            c = c + 1
    if c == (b2 - a2 + 1):
        print(-1)