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 JavaScript (node.js v5.12) (judge verdict: Accepted)

"use strict"
function main(arg) {
    var data = arg.trim().split("\n")[0].split(" ").map(Number)
    var A = data[0]
    var B = data[1]
    var a = A / 0.08
    var b = B / 0.10
    var c = Math.floor((a + b) / 2)
    var start = (c  - 10) > 0 ? c - 10 : 0 
    var end = c  + 10
    // console.log(c)
    for (var i = start; i < end; i++) {
        var _a = Math.floor(i * 0.08)
        var _b = Math.floor(i * 0.1)
        // console.log([i,_a,_b])
        if (_a === A && _b === B) {
            console.log(i)
            return
        }
    }
    console.log(-1)
}
main(require('fs').readFileSync('/dev/stdin', 'utf8'));