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++ (GCC 9.2.1) (judge verdict: Wrong Answer)

/*
 * Author : Sadi
 * Mon 20/07/2020
 * 16:39:14.89
 */
#include <bits/stdc++.h>

using namespace std;

#define    watch(x); cout << "\n" <<  #x << " is: " << x << "\n";
#define    all(a) (a).begin(), (a).end()
#define    fi first
#define    se second

template<class A, class B>
ostream& operator << (ostream& output, const pair<A, B>& p) {
    output << "(" << p.first << ", " << p.second << ")";
    return output;
}

template<class A>
ostream& operator << (ostream& output, const vector<A>& a) {
    output << "[";
    for(auto it = a.begin(); it != a.end(); ++it) {
        if(it != a.begin()) {
            output << ", ";
        }
        output << *it;
    }
    output << "]";
    return output;
}

using lld = long long;
using pii = pair<int, int>;
using pll = pair<lld, lld>;

//const int inf = 1e9;
//const int mod = 1e9 + 7;
//const double PI = acos(-1.0);
//const int mx = 1e5 + 5;



int main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
#ifndef ONLINE_JUDGE
//    freopen("input.txt", "r", stdin);
//    freopen("output.txt", "w", stdout);
#endif // ONLINE_JUDGE

    int A, B;
    cin >> A >> B;
    if(__gcd(A, B) == 1) {
        cout << -1 << "\n";
        return 0;
    }
    for(int i = 10; i <= 1000; ++i) {
        if((int) (i * .08) == A && (int) (i * .1) == B) {
            cout << i << "\n";
            return 0;
        }
    }
    // int low = 10, high = 1000;
    // int mid;
    // while(low <= high) {
    //     mid = low + (high - low) / 2;
    //     cout << mid << endl;
    //     if((mid * .08 > A) && (mid * .1 > B)) {
    //         high = mid - 1;
    //     }
    //     else if ((mid * .08 < A) && (mid * .1 < B)) {
    //         low = mid + 1;
    //     }
    // }

    // cout << low << endl;
    return 0;
}