import java.util.*;
import java.math.*;
import java.text.*;

public class Main {
    private static Scanner sc = new Scanner(System.in);
    public static void main(String[] args) throws Exception {
        int n = sc.nextInt();
        
        if (n%2==0) {
            System.out.println(n);
        } else {
            System.out.println(n-1);
        }
    }
}