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: Accepted)

    #include<bits/stdc++.h>
    using namespace std;
    #define fo(i,a,n) for(i=a;i<n;i++)
    #define ll long long
    #define deb(x) cout << #x << "=" << x << endl
    #define pb push_back
    #define mp make_pair
    #define ff first
    #define ss second
    #define all(x) x.begin(), x.end()
    #define clr(x) memset(x, 0, sizeof(x))
    #define sortall(x) sort(all(x))
    #define sortrev(x) sort(all(x),greater<int>())
    #define pi 3.1415926535897932384626

    typedef pair<int,int> pii;
    typedef pair<ll, ll> pl;
    typedef vector<int>	vi;
    typedef vector<ll>	vl;
    typedef vector<pii>	vpii;
    typedef vector<pl>	vpl;
    typedef vector<vi>	vvi;
    typedef vector<vl>	vvl;
    typedef vector<double> vd;


    const int mod = 100000007;
    const int inf = 100000005;
    const int N = 200005, M = N;
    int i,j,n,m;

    ll cnt , idx;
    vi temp;


    void solve() {
       ll x,y;
       cin>>x>>y;

       ll aa,bb;
       bool f = 0;
       fo(i,0,2001) {
         double a = i * 0.08;
         double b = i * 0.10;

         aa = (int)(a);
         bb = (int)(b);
         if(aa == x && bb == y) {
            f = 1;
            cout<<i<<"\n";
            break;
         }
       }
       if(!f) cout<<"-1\n";

    }

    int main() {
        ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);

        int t = 1;
        //cin >> t;
        while(t--) {
          solve();
        }

        return 0;
    }