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


public class Pro4
{
    public static void main(String Args[]) throws IOException
    {
        
    Scanner kb = new Scanner( new File("DATA4.txt"));
    PrintWriter xyz = new PrintWriter (new BufferedWriter (new FileWriter("OUT4.txt")));
    for (int q=0;q<5;q++)
    {
        
    Map <Character, Integer> all = new TreeMap<Character, Integer>();
    
    String s = kb.nextLine();
    ArrayList<Character> ans= new ArrayList <Character>();
    
    for (int x=0;x<s.length();x++)
    {
        Integer count= all.get(s.charAt(x));
        if (count==null)
        {
            all.put(s.charAt(x),1);
            ans.add(s.charAt(x));
        }
        else
        {
            all.put(s.charAt(x),++count);
            Character a= s.charAt(x);
            ans.remove(a);
        }
    }
        
    xyz.println(ans.get(0));
    
}
xyz.close();
}

}