using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ABC128A
{
    class Program
    {
        static void Main(string[] args)
        {
          
            {
                var word = Console.ReadLine().Split();
                double a = double.Parse(word[0]);
                double b = double.Parse(word[1]);
                double max;
                max = (a * 3 + b) / 2;
                Console.WriteLine(max);
                Console.ReadKey();



            }
        }
    }
}
    
