import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.LinkedList;
import java.util.List;

public class Ordered {

	private static boolean isOrderedWord(String word){
		char[] sortedWord = word.toCharArray();
		Arrays.sort(sortedWord);
		return word.equals(new String(sortedWord));
	}
	
	public static void main(String[] args) throws IOException{
		List<String> orderedWords = new LinkedList<String>();
		BufferedReader in = new BufferedReader(new FileReader(args[0]));
		while(in.ready()){
			String word = in.readLine();
			if(isOrderedWord(word)) orderedWords.add(word);
		}
		in.close();
		
		Collections.<String>sort(orderedWords, new Comparator<String>() {
			@Override
			public int compare(String o1, String o2) {
				return new Integer(o2.length()).compareTo(o1.length());
			}
		});
		
		int maxLen = orderedWords.get(0).length();
		for(String word: orderedWords){
			if(word.length() == maxLen){
				System.out.println(word);
			}else{
				break;
			}
		}
	}
}