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 PyPy3 (2.4.0) (judge verdict: Accepted)

def main():
    #from sys import stdin, setrecursionlimit
    #setrecursionlimit(10**9)
    #r = input()
    #n = int(input())
    #a, b = map(int, input().split())
    #s, y = input().split()
    #a = input().split()
    #a = [int(input()) for i in range(n)]
    #a = list(map(int, input().split()))
    #a = [list(map(int, input().split())) for i in range(n)]
    #a = [int(s) - 1 for s in input().split()]
    #l=[int(input()) for _ in range(int(input()))]
    #res = 0
    from math import floor
    a, b = map(int, input().split())
    ax = 0
    bx = 0
    for i in range(1,1500):
        ax = floor(i * 0.08)
        bx = floor(i * 0.1)
        if ax == a and bx == b:
            print(i)
            return 0
    print(-1)

if __name__ == '__main__':
    main()