source_code: import java.util.Scanner;
  
  public class MainA {
      public static void main(String[] args) {
          Scanner sc = new Scanner(System.in);
          int n  = sc.nextInt();
          
          int count = 0;
          
          count = n/2;
          
          count = count + (n - n/2);
          
          n = n - n/2;
              
          count = count + n;  
  
          
          System.out.println(count);
          
      }
  }
  