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: Accepted)

/********************************
* AUTHOR:  ARNAB SEN             *
* NICK  :  arnab1729             *
* INSTITUTION: IIEST, SHIBPUR    *
********************************/

#include<bits/stdc++.h>

using namespace std;

typedef string                         STR;
typedef long long                      LL;
typedef long double                    LD;
typedef unsigned long long             ULL;
typedef vector<int>                    VI;
typedef priority_queue<int>            PQI;
typedef vector<LL>                     VLL;
typedef vector<ULL>                    VULL;
typedef vector<STR>                    VS;
typedef vector<char>                   VC;
typedef pair<int,int>                  PII;
typedef pair<LL,LL>                    PLL;
typedef pair<STR,int>                  PSI;
typedef pair<int,STR>                  PIS;
typedef vector<PII>                    VII;
typedef map<int,int>                   MII;
typedef map<LL,LL>                     MLL;
typedef map<STR,int>                   MSI;
typedef map<char,int>                  MCI;
typedef map<int,STR>                   MIS;
typedef set<STR>                       SS;
typedef set<int>                       SI;
typedef set<LL>                        SLL;

#define FF                             first
#define SS                             second
#define PB                             push_back
#define PF                             push_front
#define MP                             make_pair
#define all(a)                         (a).begin(), (a).end()
#define dec(n)                         cout<<fixed<<setprecision(n);
#define f(i, n)                        for(LL i=0; i<n; i++)
#define fr(i,n)                        for(LL i=n-1; i>=0; i--)
#define fsort(a)                       sort(a.begin(), a.end())
#define rsort(a)                       sort(a.rbegin(), a.rend())


#define fast ios_base::sync_with_stdio(false),cin.tie(0),cout.tie(0);srand(time(NULL))

template<class T>  T maxT(T a, T b){return (a>b?a:b);}
template<class T>  T minT(T a, T b){return (a<b?a:b);}
template<class T>  void setmin(T &a, T b){a=(a>b ?a:b);}
template<class T>  void setmax(T &a, T b){a=(a<b ?a:b);}

void fileio(){
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
    freopen("debug.txt", "w", stderr);
}

void ofileio(){
  freopen("input.txt","r", stdin);
  freopen("output.txt", "w", stdout); 
}

void clock_out(){
  cerr<<"\nTime Elapsed : " << 1.0*clock() / CLOCKS_PER_SEC << " s\n";
}


void debug_out() { cerr << endl; }

template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
  cerr << " " << H;
  debug_out(T...);
}
 
#ifndef ONLINE_JUDGE
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#define fio() fileio()
#define ofio ofileio()
#define clock() clock_out()
#else
#define debug(...) 1
#define fio() 1
#define ofio() ofileio()
#define clock() 1
#endif

const LL MOD     = 1000000007;
const LL SIZE    = 100000;
const int INF    = 0x3f3f3f3f;
const LL LL_INF  = 0x3f3f3f3f3f3f3f3f;
const LD PI      = acos(-1);
const LL MAXN    = numeric_limits<LL>::max();

void solve(){
  LD a, b;
  cin>>a>>b;
  for(LD i=1; i<=2000; i++){
    if(floor(i*0.08) == a && floor(i*0.1) == b){
      cout<<i;
      return;
    }
  }
  cout<<-1;
}

int main(){
  fast;
  //fio();

  LL t=1;
  //cin>>t;
  while(t--){
      solve();
  }
  clock();
  return 0;
}