/* package whatever; // don't place package name! */

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
	
	 String s = "abcd";
	
		System.out.println(makeSmallestPalindrome(s));
	}
	
	static String makeSmallestPalindrome(String s) {
      
      int n = s.length();

      int start = 0;

      int end = s.length()-1;

      char [] str = s.toCharArray();

      while(start < end){
        if(str[start] != str[end] ){
          
          char small = str[start] < str[end] ? str[start] : str[end];
          
          str[start]=small;
          str[end] = small;
        }
        start++;
        end--;
      
      }


    return new String(str);
    }
}