import java.util.Scanner;


class No_192 {
	public static void main(String args[]) {
		Scanner stdIn = new Scanner(System.in);	
		int num = stdIn.nextInt();
		if (4 <= num) {
			if (num % 2 == 0) {
				System.out.println(num);
			} else {
				System.out.println(num-1);
			}
		}
	}
}