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# (Mono 4.6.2.0) (judge verdict: Accepted)

/*********************************************
* 20.05.08 AtCoder Beginner Contest 158. A, B, C
* 
*
*********************************************/
/*********************************************
::test input::
*********************************************/

namespace TempName{
    using System;
    using System.Linq;
    using System.Collections.Generic;
    using System.Reflection;
    using static System.Console;
    using static IOmacro.CsharpInput; 
    using static IOmacro.CppInput;
    using static IOmacro.CConst;
    

    public class CRun{
        public readonly char problem_num = 'C';
        
        public void solve_1() {
            //A. Station and Bus
            
            string input = _string;
            
            string ans = "No";
            for (int i = 1; i < input.Length; i++) {
                if (input[i] != input[i-1]) {
                    ans = "Yes";
                    break;
                }
            }
            WriteLine(ans);
        }
        
        public void solve_2() {
            //B. Count Balls
            
            long N = cin, A = cin, B = cin;
            
            long x = N / (A + B);
            long y = N % (A + B);
            
            long ans = 0;
            ans += x * A;
            ans += (y > A ? A : y);
            WriteLine(ans);
        }
        
        public void solve_3() {
            const double rate_A = 0.08;
            const double rate_B = 0.10;
            
            long tax_A = cin, tax_B = cin;
            long min = 0;
            long max = 3700;
            long ans = -1;
            
            while (min +1 < max) {
                long temp = min + max >>1;
                
                
                long chk_A = (long)(rate_A * temp);
                long chk_B = (long)(rate_B * temp);
                
                if (chk_A < tax_A || chk_B < tax_B) {
                    min = temp;
                }
                else {
                    max = temp;
                }
            }
            
            if ((long)(max * rate_A) == tax_A && (long)(max * rate_B) == tax_B) {
                WriteLine(max);
            }
            else {
                WriteLine("-1");
            }
        }
    }
    
    class Program { 
        static void Main() { 
            var run = new CRun();
            if (run.problem_num == 'A') run.solve_1(); 
            if (run.problem_num == 'B') run.solve_2(); 
            if (run.problem_num == 'C') run.solve_3();
        } 
    }
}

namespace IOmacro {
    //20.05.08. 수정
    
    using System; 
    using System.Linq; 
    using System.IO;
    using System.Collections.Generic;
    
    public class CsharpInput {
        public static StreamWriter _writer = new StreamWriter(Console.OpenStandardOutput());
        public const char separator = ' ';
        public static string _string{get{return Console.ReadLine();}}
        public static string[] _stringa{get{return (Console.ReadLine().Split(separator));}}
        public static int _int{get{return int.Parse(Console.ReadLine());}}
        public static int[] _inta{get{return Console.ReadLine().Split(separator).Select(int.Parse).ToArray();}}
        public static long _long{get{return long.Parse(Console.ReadLine());}}
        public static long[] _longa{get{return Console.ReadLine().Split(separator).Select(long.Parse).ToArray();}}    
        public static double _double{get{return double.Parse(Console.ReadLine());}}
        public static double[] _doublea{get{return Console.ReadLine().Split(separator).Select(double.Parse).ToArray();}}    
    }
    
    public class CConst {
        public static readonly int MINI = int.MaxValue;
        public static readonly long INF = Int64.MaxValue;
    }
    
    public class CppInput {
        public static CppInput cin => new CppInput();
        public const char separator = ' ';
        private static readonly Queue<string> _input = new Queue<string>();
        private CppInput(){}
        public static implicit operator string(CppInput _) {
            if (_input.Count == 0) Console.ReadLine().Split(separator).foreachExtension(x => _input.Enqueue(x));
            return _input.Dequeue();
        }
        public static implicit operator int(CppInput _){
            if (_input.Count == 0) Console.ReadLine().Split(separator).foreachExtension(x => _input.Enqueue(x));
            return int.Parse(_input.Dequeue());
        }
        public static implicit operator long(CppInput _){
            if (_input.Count == 0) Console.ReadLine().Split(separator).foreachExtension(x => _input.Enqueue(x));
            return long.Parse(_input.Dequeue());
        }
        public static implicit operator double(CppInput _){
            if (_input.Count == 0) Console.ReadLine().Split(separator).foreachExtension(x => _input.Enqueue(x));
            return double.Parse(_input.Dequeue());
        }
    }
    
    public static class EnumerableExtension {
        public delegate void Function<in T>(T val);
        public static void foreachExtension<T>(this IEnumerable<T> enumerable, Function<T> function) {
            foreach (var x in enumerable) function(x);
        }
    }
}