source_code: import java.util.Scanner;
  
  /**
   * Created by IntelliJ IDEA.
   * User: Administrator
   * Date: 13.05.11
   * Time: 23:21
   * To change this template use File | Settings | File Templates.
   */
  public class ToyArmies {
      public static void main(String[] args) {
          Scanner in = new Scanner(System.in);
          long n = in.nextLong();
          System.out.print(String.format("%d",(long)(n*1.5)));
      }
  }
  