import java.net.*;
import java.io.*;
import java.util.*;

class Four {
	public static void main(String args[]) throws IOException {

		ServerSocket ss = new ServerSocket(25000);
		Socket s = ss.accept();
		Scanner sc = new Scanner(s.getInputStream());
		PrintWriter pw = new PrintWriter(s.getOutputStream(),true);
		pw.println(sc.nextInt()*2);
		}
}