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 C++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include<iostream>
#include<vector>
#include<string>
#include<algorithm>
#include <cmath>

using namespace std;
const long long INF = (long long) (1e18)+1;

int main() {
  int a;
  int b;
  cin >> a >> b;
  int Y_1_MIN = a / 0.08;
  int Y_2_MIN = b / 0.1;
  cout << Y_1_MIN << endl;
  cout << Y_2_MIN << endl;

  int Y_1_MAX = (a+1) / 0.08;
  int Y_2_MAX = (b+1) / 0.10;

  if (Y_2_MIN <= Y_1_MIN && Y_1_MIN < Y_2_MAX ) {
    cout << Y_1_MIN << endl;
  } else if (Y_1_MIN <= Y_2_MIN && Y_2_MIN < Y_1_MAX) {
    cout << Y_2_MIN << endl;
  } else {
    cout << -1 << endl;
  }
  return 0;
}