import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;

class Main {
	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		int num=Integer.parseInt(br.readLine());
		br.close();
		PrintWriter out=new PrintWriter(System.out);
		if(num%2==0){
			out.println(num);
		}else{
			out.println(num-1);
		}
		out.flush();
	}
}