source_code: import java.util.Scanner;
  
  
  public class A_Toy_Army {
  
  	/**
  	 * @param args
  	 */
  	public static void main(String[] args) {
  		// TODO Auto-generated method stub
  		Scanner entrada = new Scanner(System.in);
  		while(entrada.hasNextInt())
  		{
  			int n = entrada.nextInt();
  			System.out.println(n+(n/2));
  		}
  	}
  
  }
  