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 <bits/stdc++.h>
#include <ctime>
#include <sstream>
#define weewoo ios::sync_with_stdio(false);cin.tie(0)
#define pii pair<int,int>
#define pll pair<ll,ll>
#define ld long double
#define ll long long
#define se second
#define fi first
#define ctoi(x) (x-'0')
#define pi (acos(-1))
#define llputin(a,n) for(int i=0;i<n;i++){ll x;cin >> x;a.push_back(x);}
#define iputin(a,n) for(int i=0;i<n;i++){int x;cin >> x;a.push_back(x);}

#define MOD ((ll) 1e9 + (ll) 7)
using namespace std;

ll pw(ll x,ll a){
    if(a==0)
        return 1;
    ll t = pw(x,a/2);
    if(a%2==0)
        return (t*t);
    else
        return (t*t*x);
}

bool prime(int x)
{
    if(x < 2) return false;
        for(int i=2; i<= sqrt(x); i++) {
            if ((x%i) == 0) return false;
        }
    return true;
}

bool cmp(const pair<int , int> &a , const pair<int , int> &b){
    return (a.first < b.first);
}



int main()
{
    weewoo;ll a,b;
    cin >> a >> b;
    ll cur = a*100;
    cur/=8;
    if(cur/10 == b)
        cout << cur << endl;
    else
        cout << -1 << endl;
    return 0;
}