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)

#include <bits/stdc++.h>
#include <math.h>
#include <cmath>

using namespace std;
using ll =long long;
using vi = vector<int>; 
using vvi = vector<vi>; 
using vl = vector<ll>; 
using vvl = vector<vl>; 

#define rep(i,n) ;for( int i =0; i < n ; i ++)

bool is_int_lround(double x){
  return std::lround(x)==x;
}
int ketasuu(int x){
  int n=0;
  while(x>0){
    x /=10 ;
    n ++;
  }
  return n;
}
ll gcd11(ll x, ll y){
  long long a= max(x,y), b=min(x,y), c=a%b;
  while( c!=0){
    a =b;
    b =c;
    c = a%b;
  }
  return b;
}

int abs(int x, int y){
  if(x>=y){
    return x-y;
  }
  else if(y>x){
    return y-x;
  }
}
int fiv(int n){
  if(n==0){
    return 0;
  }
  else if(n==1){
    return 1;
  }
  return fiv(n-1)+fiv(n-2);
}
ll conbi(int n,int m){
  
  cin>>n>>m;
  vector<ll> a(100);
  a[0] =1;
  for(int i=0;i<14;i++){
    a[i+1]=a[i]*(i+1);
  }
  return a[n] /(a[m] *a[n-m]);
}
int main(){
  int a,b;
  cin>>a>>b;
  bool res =false;
  rep(i,10001){
    if((int)(i*0.08) ==a && (int)(i*0.10) ==b){
      cout << i<<endl;
      res =true;
      break;
    }
  }
  if(!res) {
    cout<<-1<<endl;
  }
  
}