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)
        {
            int a, b, c, d;

            var word = Console.ReadLine().Split(' ');
            a = int.Parse(word[0]);
            b = int.Parse(word[2]);

            c = (3 * a) + b;

            d = c / 2;

            Console.WriteLine(d);

            Console.ReadKey();





        }
    }
}