import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sc = new Scanner (System.in);
		int a = sc.nextInt();
		System.out.print(qingWa(a));
		
	}
	public static int qingWa(int a) {
		int n = 0;
		for (int i=1;i<=a;i++) {
			n=n+3;
		}
		return n;
	
	}

}

/**************************************************************
	Problem: 1596
	User: admin
	Language: Java
	Result: Accepted
	Time:774 ms
	Memory:40364 kb
****************************************************************/