package com.javarush.task.task18.task1803;

import java.io.FileInputStream;
import java.io.*;
import java.util.*;

/*
Самые частые байты
*/

public class Solution {
    public static void main(String[] args) throws Exception {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        FileInputStream stream = new FileInputStream(reader.readLine());
        ArrayList<Integer> array = new ArrayList<Integer>();

        Set<Integer> arrayx = new HashSet<Integer>();

        int k = 0;
        int max = 0;
        if(stream.available()>0){
            array.add(stream.read());
        }

        Collections.sort(array);
        for(int  i = 0; i < array.size(); i++){
            if(array.get(i)==array.get(i+1)){
                k++;
            }
            else{
                k=0;
            }
            if(k==max && array.get(i+1)!=array.get(i+2)){
            arrayx.add(array.get(i));
            }
            if(k>max){
                arrayx.clear();
                max = k;
                arrayx.add(array.get(i));
            }

        }
        for(int g : arrayx){
            System.out.print(g+" ");
        }


        reader.close();
        stream.close();
    }
}