import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        Run run = new Run(scanner);
    }
}

interface General {
    default void sp(Object... o) {
        int i;
        final int end = o.length - 1;
        for (i = 0; i < end; i++)
            System.out.print(o[i] + " ");
        System.out.println(o[i]);
    }
}

class Run implements General {
    Run(Scanner scanner) {
        long measure = scanner.nextLong(), max = 0;
        for (int count = 0; count < measure; count++) {
            long current = scanner.nextLong();
            if (isHW(current) && current > max)
                max = current;
        }
        System.out.println(max);
    }

    boolean isHW(long number) {
        char[] ones = String.valueOf(number).toCharArray();
        boolean is = true;
        for (int left = 0, right = ones.length - 1; left <= right; left++, right--)
            if (ones[left] != ones[right]) {
                is = false;
                break;
            }
        return is;
    }
}