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)

import math
import random
import sys

MAX_INT = 2**62-1
sys.setrecursionlimit(10**7)

input = sys.stdin.readline


def read_n_int():
    return map(int, input().split())


def main():
    a, b = read_n_int()
    num1, num2 = a / 0.08, b / 0.1
    s1 = set()
    i = 0
    while int(num1*0.08) == int((num1+i)*0.08):
        s1.add(int(num1+i))
        i += 1
    i = 0
    s2 = set()
    while int(num2*0.1) == int((num2+i)*0.1):
        s2.add(int(num2+i))
        i += 1
    # print(s1, s2)
    if s1 & s2:
        print((s1 & s2).pop())
    else:
        print(-1)


if __name__ == "__main__":
    main()