Even

import java.util.*;
public class Test3 {


    public static void main(String[] args) {
        Scanner reader = new Scanner(System.in);
        StringBuffer toBeModed = new StringBuffer(reader.nextLine());
        toBeModed.deleteCharAt(toBeModed.length()-1);
        String[] input = toBeModed.toString().split(" ");
        maxeven(input);
    }

    public static void maxeven(String[] input) {
        long currentEven;
        long max=-1;
        for (int i = 0; i <input.length ; i++) {
            if(String.valueOf(input[i].charAt(0)).equals("0")||
                    String.valueOf(input[i].charAt(0)).equals("1")||
                    String.valueOf(input[i].charAt(0)).equals("2")||
                    String.valueOf(input[i].charAt(0)).equals("3")||
                    String.valueOf(input[i].charAt(0)).equals("4")||
                    String.valueOf(input[i].charAt(0)).equals("5")||
                    String.valueOf(input[i].charAt(0)).equals("6")||
                    String.valueOf(input[i].charAt(0)).equals("7")||
                    String.valueOf(input[i].charAt(0)).equals("8")||
                    String.valueOf(input[i].charAt(0)).equals("9"))
            {
                if(Integer.parseInt(input[i])%2==0){
                    currentEven= Integer.parseInt(input[i]);
                    if(currentEven>max){
                        max = currentEven;
                    }
                }
            } else {
                continue;
            }
        }
            System.out.println(max);
    }
}