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

namespace ConsoleApp107
{
    class Program
    {
        static void Main(string[] args)
        {
            double n = int.Parse(Console.ReadLine());
            n = n * 1.5;
            int N = (int)n;
            Console.WriteLine(N);
            Console.ReadLine();
        }
    }
}